I know I have asked similar questions in the past but lets go for yet another variation on the theme.
 
Amazon has the EVGA 780Ti 3GB VRam Superclocked with the reference cooler for $689.99 and a $10 rebate right now. Free two day shipping with my Prime account. I am tempted but I have to wonder if I would not bee better off to wait for the higher end Maxwell cards to be released. My GTX 680 2GB VRam does the job right now. It's only failing is with Skyrim heavily modified with texture mods, it runs out of VRam from time to time.
 
Aside from rare Skyrim issues the 680 is fine. That being said I am debating about upgrade my i5-3570k to a i7-3770k for HT and add in a pair of stock 750Ti's for crunching for $623.97 before shipping and taxes instead of going the 780Ti route.
 
The i7-3770k will work in my current Motherboard and I think my Cooler Master Gemin II CPU cooler will do a good job with the i7.
 
Here is my current system that I want to maximize for crunching while being able to play games from time to time. Yet not have to build a totally new system.
 
Intel Core i5-3570K Ivy Bridge 3.4GHz (3.8GHz Turbo) LGA 1155 77W Quad-Core Desktop Processor Intel HD Graphics 4000 BX80637I53570K
ASUS P8Z77-V LK LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS
CORSAIR Vengeance LP 32GB (4 x 8GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory
EVGA 02G-P4-2680-KR GeForce GTX 680 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card
2x SAMSUNG 830 Series MZ-7PC512D/AM 2.5" 512GB SATA III MLC Internal Solid State Drive (SSD) Desktop Upgrade Kit
Seagate Barracuda ST1000DM003 1TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive
SeaSonic Platinum Platinum-860 860W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS PLATINUM Certified Full Modular Active PFC Power Supply
SAMSUNG DVD Burner 24X DVD+R 8X DVD+RW 8X DVD+R DL 24X DVD-R 6X DVD-RW 16X DVD-ROM 48X CD-R 24X CD-RW 48X CD-ROM SATA
Corsair Special Edition White Graphite Series 600T Steel / Plastic ATX Mid Tower Computer Case
COOLER MASTER GeminII S524 120mm Long Life Sleeve CPU Cooler
 
Comments or suggestions?

If your goal is to simply upgrade rather than build new then I think you are on the right track.  So far the 750Ti is working out well for me and I have definitely seen a nice boost in my crunching output with a minimal increase in power usage.
On the other hand, will a 780Ti give you more crunching performance than an upgraded CPU and two 750Ti's?  That I don't know.

The 780Ti is a beast! You'll love it! Cause I sure love mine!

I have a 3770k at 4.4 ghz.... this recent pg challenge, my tasks were finishing around 45-50 min.... what were your times?
I have the h100 on it, it topped out at 60c using all 8 threads in a closet with no air circulation with the door slightly open....

You have more ram than me, i wonder tho much that plays into it, as well as the temps.... Im not around when the temp could be goin above 60c and triggering an oc downthrottle....
Were your pps tasks saying p ps llr 6.24?

Either way, worst case you only double your output by gaining by with the 3770k upgrade....

It was on.... times did improve a bit from the old version of p ps, by about 30 min a task....

Thanks for the info linuxrouter. I am still debating it. The reports of coil whine and not crunching at full capacity on some projects are making me hesitate.

I feel the itch to buy a 780 Ti Superclocked, just lack the funds! 
 
* Scrounges in couch cushions for loose change, finds only lint *

I guess I will be seeing how well my Platinum 860 watt Seasonic PSU will handle the load. I am planning on keeping my 680 in the system as well.
 
I just need to figure out how to set one GPU to one project and the other to a different project when the mood hits me.

It will blow Your socks off Khali

OK, its installed and the 780 Ti and crunching away on GPU Grid. I moved the 680 down to my second PCI E slot and its crunching away as well. I may have to relocate my PC since it sounds like a jet engine with both GPU fans running. The fan curve I set up for my 680 does not do the job for the 780 Ti and I can't figure out how to set up a second one for the 780 using EVGA Precision. Not sure it was meant for two cards of different models. I have to set the 780 to 85% fan speed to keep it below 80 C. I may have to remove the side window in my Corsair 600T case and install the mesh grill that came as a option to let more air into the case right by the GPU fans.
 
After 30 minutes run time the 780 Ti is at 9% and the 680 is at 5% on GPU Grid Long Run tasks that both started at the same time.
 
Any one know how or if you can run one project on the 780 Ti and a different project on the 680? Or do I have to stick with the same project on both GPU's?
 
Edit: I just noticed I lose a CPU core with both GPU's running. Which did not surprise me much.

Thanks linuxrouter!!!

 
I already had the config change for multiple GPU's in place. But the exclude GPU portion of that will come in handy.

One last thing before I let this thread die.
 
Yesterday I had my first one million point day in GPU Grid with a grand total of 1,047,900 in GPU Grid for the day! 
 
*Khali bounces around the room doing The Happy dance*

Yeah, I see you place some very decent numbers on GPUGrid these days.
Happy for you Khali
As I said in another post, "I think we will get our 3 GpuGrid points back soon..... Very soon^^"