cpu should be more than fine I am happy with my AMD for a long time. It overclocks like a dream in my watercooled gaming rig. Another thing might be the motherboard itself. Also try uninstalling the nvidia driver normally and then use driver cleaner(free in utilities downloads at 3d guru. After that use a good registry cleaner , CCleaner is awsome(free). Lastly use a good HDD defrager to completely defragment your system I use O&O 10 professional. Has gaming specific optimizations for defraging. Once that helped me out with F.E.A.R Multiplayer glitching.
http://s610.photobucket.com/albums/tt181/tehreaver/?action=view¤t=00005.jpg There, that should work, have a look.
Is Darkfall the only game you have tested it on? If so, you need to test it on other games. In the Tropics that I had you download your system scored higher than mine.
Don't worry, it is not that bad for games. I am still gaming at high details any game including crysis with my opteron 170 and 8800 GTX (however I bought yesterday a GTX 260 as they are now so cheap that I couldn't resist the temptation) you must have a problem with the drivers or the card itself. Bad PSU also give bad games performance and crashes but you don't mention this, what brand is yours? By the way, have you tried reinstalling the game?
My suggestion is to download EVGA Precision basicly for the graphs then, while running EVGA play a game a minute or so then immediatly go back to EVGA & see if your GPU does indeed jump up to 3D or is locked in 2D. The graphsdont lie, if its going into 3d mode you will see a major speed spike in the shader & mem graps. If the graphs remain flatline RMA the card back. You probably should check to see that you are receiving power thru both PS plugs to 260 with a Vmeter probably just to be sure thats not a prob. PS- When I installed my 260 I didnt remove any previous drivers just installed my 260 & then went to Nvidias site & downloaded the latest driver. Pc of cake, just took 1 restart. Unless one is changing from an ATI to a Nvidia wont matter deleting drivers. Your simply upgrading them. My money is telling me drivers are the least of your problems.
You could also run this 3D App in a resizable window and observe your clocks while it's actually running. No need to jump back and forth.... http://www.daionet.gr.jp/~masa/rthdribl/ Or just log them with Rivatuner. The above would be easier of course if you're not familiar with Rivatuner.
It does show my one CPU capping with BOTH different Cards in , even with the 8800 gts 320mb, can anyone help any further? Or do I need a new processor?