I had a 570GTX and decided to grab a 680GTX to get better preformane with nvidia 3D.
I currently have both the 680 and 570 in my rig so I can use more than 2 screens, but my main question is should I set the 570 to a dedicated physx card or let the 680 do all the work (well, under auto select). My specs are below. I tried to do a serch on this topic but came up with nothing and I plan on doing testing but wanted to check and see if anyone else has the data before I dedicate an afternoon of pulling the card / tring it in the 3rd PCIe slot / trying the 680 solo.
CPU - i5 2500k (OC 4.8ghz)
RAM - CORSAIR Vengeance 8GB
MB - ASUS P8Z77-V DELUXE
GPU1 - EVGA SuperClocked 02G-P4-2682-KR GeForce GTX 680
GPU2 - EVGA 570 GTX (unknowen M/N at this time, got in store at tigerdirect a wile back)
SSD - 120gig OCZ
HDD - handful of WD Black and greens
PSU - 850w CORSAIR
If you need any more info, let me know. I am currently at work but I can remote into my home desktop if CPUz or something similar is required.
quick update, doing a bit more reading on my MB, I am 90% sure that the most gain I can get will be the 570 in the x4 (3rd PCIe) slot. I still don't know if it is beneficial to have it as the dedicated physx card however.
Edit ~ I def want to keep the 2ed card for no other reason than I want to be able to run 4 screens, my main gaming screen, TV, 2 19in side screens.
i have basically the same systems as you and just ordered a 680 to replace my current 570 and am going to keep the 570 to run physx as it will give a performace increase the 680 alone can run 4 monitors but the 570 can be used to run 2 and physx to take the load off the 680 this will give a possible 20 fps gain depending on the game