Well pretty much my issue atm is my 8800GTX has suddenly stopped performing well. In Age of Conan I have gone from 60fps steady to stuttering at 2-6fps. In Team Fortress 2 I went from capping out at 70FPS constant without even a single dip, to about 15-30fps. I also get alot of aliases and sometimes my screen just completely goes jagged and I have to alt tab in and out to see anything again.
 
I can narrow this down to exactly when/kinda what caused it, I just need help fixing/figuring out what to do.  
 
About a week ago today my PSU blew in what I guess was a surge issue. I had a surge protector, but the power flicked on and off about 9 times really fast and when I went to boot up my PC the fans would start spinning slowly then die out.
 
Anyways, few days later I replace my PSU. Corsair 620hx (http://www.newegg.com/Product/Product.aspx?Item=N82E16817139002).
 
Specs:
eVGA 680i  
x6800 @ 3.3ghz
eVGA 8800GTX  
4gb G.SKILL 4GB PC2 8000
Soundblaster X-Fi
2x 150GB Raptors
1x 320GB Caviar
 
I was fine for a few days and did not notice a difference. Mainly because all I was playing was CS1.6 so I was able to run it just fine. I did get crash about 3 times though in CS which was the first wierd thing I encountered. (Screen got jagged and blah).
 
Anyways just trying to figure out what the issue could be...
 
-Cooling wise nothing should have changed, I have better airflow than before due to modular cables this time.  All my fans are working fine. Only thing I can think of atm is the side of my case is still open, but I don't believe that would be enough to overheat the card? Room temp is also same.
 
-Power wise obviously I had a change. But I did enough research to know my PSU choice was good and should easily be able to handle what I have.
 
-Could the video card have also been damaged in the surge? I was worried other stuff may have fried but everything seemed okay after replacing the PSU.
 
-Reinstalled clean drivers already, not the issue.
 
Any ideas are areas I should look at first?
 
Thanks
 
 

I think you have answered your own question. Your blown PSU most likely damaged the 8800GTX. Send it back in, man!

Well I wasn't sure if a card was capable of being "half" blown up causing those kind of issues.
 
Before I commit on new card / sending this one in (if I can, it is few years old) any other opinions?

Bad video ram, either a shorted cell or damaged voltage regulation. Almost 100% confidence in internal IC electrical failure.
 
If the damage is in a non fatal location, your symptoms would be as described.