You are in a bit of a sweet spot that made the last of the 775 socket processors hard to decide between.  You have a high clock speed but only a dual core CPU.  The most expensive quad cores didn't get that fast without overclocking and the CPU I would suggest looking, the Core 2 Quad Q9550 does clock under to 2.83 GHz.  Depending on the type of games you are playing you may want a quad core, but you wont find them new and just about anything you pay more than $75 for a quad core would be too much IMO. 
 
As for graphics card, if you wanted to put more into a card, you are going to be crossing into the Kepler line of GPUs.  Some of them were built for PCIE 3.0, but dont let that scare you.  Most of the mid range cards are not using the bandwidth of 2.0 let alone 3.0.  You could jump up to a GTX760 for $250, but I would start to worry about that CPU again.
 
Here's what I would actually recommend.  If your system works the way you want it to now, leave it.  Wait till it runs into the ground and/or you are ready to replace all the main guts of your system, CPU, Motherboard, Memory, Graphics Card and possibly even HDD (replaced with an SSD) with new generation equipment.

pc master,
Thanks I upgraded to the intel q9550s , and a bit faster ram,,a world of difference.its now blazing fast,,well to me anyway.Again thanks for the advice

You can be really conservative and drop a Xeon 771 quad core in your 780i. I wouldn't even mess with core 2 quad as they are still absurdly high priced for their age. Check out the socket mod over at overclock.net. I did this mod on my 750i FTW with a xeon x5470 E0 chip and it OC's like a raped ape.
 
I run mine daily at 4.25ghz with a 1.31 vcore. Even stock they run 3.33ghz...basically an E8600 quad core. You can get a x5470 for $80 on Ebay..our a cheaper alternative the x5460 for around $40. Stock those are 3.16ghz. A x5450 aka Q9650 can be had for $30. The mod is super easy and with my current setup i can keep up with even the new AMD FX quads...or a stock 2500k depending on the application. Don't waste your money on anything other than a Xeon if your trying to breath new life into your board..it's guaranteed to work on the 780i with newest bios. Educate yourself on it and you'll thank me later
 
EDIT: I've also had this mod working on a Gigabyte EP45T-DS3R motherboard without a single issue.

stealthrt2007
You can be really conservative and drop a Xeon 771 quad core in your 780i. I wouldn't even mess with core 2 quad as they are still absurdly high priced for their age. Check out the socket mod over at overclock.net. I did this mod on my 750i FTW with a xeon x5470 E0 chip and it OC's like a raped ape.
 
I run mine daily at 4.25ghz with a 1.31 vcore. Even stock they run 3.33ghz...basically an E8600 quad core. You can get a x5470 for $80 on Ebay..our a cheaper alternative the x5460 for around $40. Stock those are 3.16ghz. A x5450 aka Q9650 can be had for $30. The mod is super easy and with my current setup i can keep up with even the new AMD FX quads...or a stock 2500k depending on the application. Don't waste your money on anything other than a Xeon if your trying to breath new life into your board..it's guaranteed to work on the 780i with newest bios. Educate yourself on it and you'll thank me later
 
EDIT: I've also had this mod working on a Gigabyte EP45T-DS3R motherboard without a single issue.

This is FANTASTIC!!!  I wish I had ran across this when I was using my 775 builds, this is the kind of tinkering I love to do. I may just put them back together and try this out, just for the fun of it. I still have a evga780i ftw, asus 750i and asus 650i. I will def let them know over in that thread if I could get it working. Big thanx for the heads up on this.  \m/

Upgraded from Q6600 @ 3,2Ghz to a Xeon e5450 @ 4,0Ghz on a 790i ultra sli last year. Temps are still lower at 4Ghz to the Q6600 at 3,2ghz . These Xeons are really nice chips.

The Xeon seems to need a different socket (lga771) ,  you can try this: http://www.delidded.com/lga-771-to-775-adapter/ .

x5470 should work on a 780i ftw.
www.delidded.com/lga-771-to-775-adapter/3/#evga