I am running x2 EVGA 550ti's in SLI with a Corsair 850 PS.I am on a budget of about $625.00 US and am wondering a few things...1)will my PS handle two 760's smoothly 2)will I see an ample performance boost in my gaming ie:BF4? 3)is it really worth it to invest in the 4Gig card verses the 2 giger? 4)will the two cards fit nicely in my ASUS Sabertooth 990FX Mobo? 5)find two 770's in my budget range? I am partial and only purchase EVGA cards...for years now and have never had a card fail yet!!!.Yes,these are most noobish questions,but  need answers plz...thx

Depending on what you want to upgrade . Are you using one Monitor and not planning on getting more then get the 770 and use one of your leftover cards as a PhysX and also get an SSD to replace your together drives take them all out and you will have no bottle necks. IMO that's what I would do.
 
Going that way wont take all your money and you wont hurt on your next upgrade. The drivers coming out have not been worthy of wasting on a 780.hit up frys they have a sale on 770 4gig 300 good deal. or here they have great deals too.
 
or if you need to look at my system I have numbers and scores. . but if your hart is set get you two 770s and yes your 850 PSU will be fine as long as you are not pushing a lot of stuff its less power then your 550s

GTX550 Ti uses 116W of power each, drawn from 12v, that is 9.6A per card at reference clocks.
GTX760 uses 170W of power each, drawn from 12v, that is 14.3A per card at reference clocks.
GTX770 uses 230W of power each, drawn from 12v, that is 19.3A per card at reference clocks.
 
Even with the pair of 770's, your PSU is still qualified.
 
Technically, GTX750 Ti succeeded GTX650 Ti which succeeded GTX550 Ti going by market segment succession, and most reviews put GTX750 Ti = GTX580 in BF4 at 37fps at 1920x1200-- but 750 Ti has no SLI option (pity, it uses way less power at 60W each or 5A drawn at 12v).   Clearly there are better cards since a single GTX760 would achieve 54fps while GTX770 would achieve 67fps.  SLI would scale better, 2-way GTX760 = GTX780 Ti (in between GTX Titan and GTX690), so you should get 87fps in BF4 on a 1920x1200 with Ultra details. 
 
 FYI, Vram usage depends on the game and choice of settings.  This review from pugetsystems suggests for up to 4K resolutions with today's games, you should have at least 2GB.  But if you won't get a resolution that big anytime soon, then you don't have to worry about more.  But, time doesn't stop and you should plan ahead for the requirements of future games over the next 1-2 years, thus 4GB would be better for later on (depends how often you upgrade).
 
Finally, I suggest you also invest in upgrading the CPU/RAM/mobo.  Unless you were GPU-bottlenecked before, getting much better graphics will not scale as expected (keeping in mind all the above linked reviews use overclocked new Intel processors, you will NOT get the same frame rates with your processor; your new graphics card investments will be held back compared to what's out there now).  You don't have to, just don't complain about expecting more.

I found two(will be running in SLI)EVGA "duel" GTX SC 770 cards within my budget.The reasoning for this particular card is the bloody price point...I am on a tight budget!But,being the uneducated gamer I am....what does "duel" stand for?I just could not see investing in two 760's with these 770's being a little more coin.

1sthurricane
I found two(will be running in SLI)EVGA "duel" GTX SC 770 cards within my budget.The reasoning for this particular card is the bloody price point...I am on a tight budget!But,being the uneducated gamer I am....what does "duel" stand for?I just could not see investing in two 760's with these 770's being a little more coin.

It bears repeating that it may not be worth the investment of getting such better graphics cards if your CPU is holing you back.  Statistically, if you're really an uneducated gamer on a tight budget, chances are we can conclude your processors is a stock AMD, which puts it way behind already.  
 

• You might as well tell us your system specs and which games you play so we can tailor fit your graphics card choices, it isn't like we wouldn't know.

 
Remember, the central processors runs your games and tells your graphics cards what to draw, the graphics card does NOT run your games.  Don't expect the performance results from any GTX770 review because they used overclocked Intel processors; it makes a giant difference, by as much as 60-70%.  What's the point of investing so much only to loose that fraction?
 

• I'd would suggest you get the pair of GTX760 and save up money for a complete platform change at some point.

 
I had a friend who used an Athlon x2 215 2.7GHz dual-core with a GTX660 and when he just changed the RAM/mobo/CPU for a new Haswell platform (not even overclocking, he went for the cheapest parts < $450), he claimed it was night and day, more than double performance without changing the graphics cards.  Granted he was playing a CPU-bound game (Total War: Rome II), while most shooters still depended on the GTX660 and didn't improve that much-- it proves the type of game matters as well.
 

• I'm just saying don't hype up the graphics card upgrade to the point of ignoring the influence of everything else.

1sthurricane
Well,I ran across a deal I could not pass up on two GTX 770'S(only 2 gigs each).Installed both in SLI,and wow they are a long card..barely fit,applied the newest Beta drivers ran Heaven with no serious  hiccups and jumped on BF4.Put my ingame video settings to just high and my frame rates are no better and sometimes worse than when I was running my two 550TI'S.As previously stated,I am an uneducated novice but I am thinking serious bottle neck with my obsolete AMD FX4100 CPU(over clocked).I have a AMD FX8350 Black Edition CPU that I will pop in when my Artic Silver comes in.I am guessing it is my CPU.Windows 7(64),ASUS Sabertooth FX990 Mobo,16 gigs of Corsair Vengeance ram,Corsair TX850 PSU,single ASUS monitor,Corsair H100 looped water cooler and multiple fans in a Azza Solano case.I run the EVGA Precision X and the one good thing is these cards are running much cooler.I was so excited with my shiny new toys,only to be frustrated once again with my lack of knowledge on how to make all the goodies work together.

don't  install beta drivers. they are beta for some reason. use the latest certified ones. ( 335 ones if not mistaken)
as for BF4?  that must be the most buggy game ever to come out into the market! from many the many games i play that thing is almost junk and it needed a LOT more work before it came out.
try other games instead.
 
try the Wicther 2 EE edition on ultra settings for a couple of hours! and if you dare turn on the UBERSampling ( i dare YA) 
 
don't forget in nvidia control panel to select maximum performance in power management option in the 3D settings TAB
 
for all the pieces to work together you should try research first.
 
o have a Q9450 Cpu running @ 3.5Ghz that bottlenecks my 760 sc BIG time. i should have had at least a 36000 score with it and only got around 21000 points in 3d mark vantage!
and still it does not let me down. BF4 is the worst game  i got in my hands! and on some badly programmed scenarios the frames were extremely low!
still with other games there is no lack of frames! even bottlenecked as it is!
 
try other games. dx 10 and dx 11 games AND upgrade your cpu as soon as you can. ;)

I love this site,information from everywhere!!!Well,popped in my new AMD FX8350 Black Edition CPU...Swapped my old ASUS Sabertooth 990FX(1st generation)MOBO for the newer GIGIBITE 990FXA UD3 MOBO and whoopie...decent frame rates all at stock settings.Had my old AMD FX4100 CPU overclocked but she just could not keep up with my two new 770's, decided to upgrade my old MOBO too and be done with it all.BF4 is really a beast on all your hardware,buggiest game I have ever played and frame rates still dip alot on some of the Naval Strike maps but my three upgrades have made it all somewhat worthwhile.Next will be overclocking my new goodies!!!!OOhhh,am running the 335 drivers,should I run the newest 337 betas?Thanks to all of you for the help,we uneducated gamers would be lost without your direction .

1sthurricane
I love this site,information from everywhere!!!Well,popped in my new AMD FX8350 Black Edition CPU...Swapped my old ASUS Sabertooth 990FX(1st generation)MOBO for the newer GIGIBITE 990FXA UD3 MOBO and whoopie...decent frame rates all at stock settings.Had my old AMD FX4100 CPU overclocked but she just could not keep up with my two new 770's, decided to upgrade my old MOBO too and be done with it all.BF4 is really a beast on all your hardware,buggiest game I have ever played and frame rates still dip alot on some of the Naval Strike maps but my three upgrades have made it all somewhat worthwhile.Next will be overclocking my new goodies!!!!OOhhh,am running the 335 drivers,should I run the newest 337 betas?Thanks to all of you for the help,we uneducated gamers would be lost without your direction .

 
Definitely run the Beta. It is a good driver.  I can't wait to see the WHQL get released.