That PSU is "big enough" but the brand isn't exactly known for producing hi end PSU's.
Download OCCT and run the GPU and CPU tests ..... monitor the temps and voltages throughout the tests (software will produce graphs at end). You don't want voltages to vary my more than 3% (ATX spec is 5% but issues can occur above 3) nor temps to get to a point to make your GFX card / CPU cranky.
Just experiencing below average framerates in my games would be the major symptoms.
In Black Ops multiplayer it's most apparent, and I also experience some hitching in the game. Getting to as low as 35FPS in some places.
BC2, it's just not as smooth as it should be.
And, I don't know if it's just my brain tricking me or not, but it almost seems as though the draw distance on detail props and stuff like that is below average. Some entities don't "pop-in" until I'm fairly close.
Everything was running fine when I first installed the video card in late December. Then after about a month I noticed the performance decrease. I reformatted to fix the issue. It was fixed, but the problem eventually returned. I think I've reformatted about 3 times in a desperate attempt.
Different video driver versions, and Restoring default nVidia settings.
Reinstalling sound drivers.
Reinstalling ethernet drivers.
After reformatting, I first installed Black Ops. Then I installed all of my necessary applications & programs, one-by-one, to see if there was some kind of conflicting problem there.
Checked startup programs.
Checked services running in the background.
Ran Memtest on each stick of RAM with about 6 passes.
Ran Prime95 to see if I could get any errors.
On OCCT, the area for 12V is disabled, therefore it doesn't generate a graph based on 12V:
One thing I can show you guys is my unstable frame rate...
For example, one minute it will be micro-fluctuating around 45 fps, then around 60fps, and back to ~45, so on and so forth. Same area, not moving and nothing going on. It doesn't happen in all areas all of the time, but it does happen. This goes on across most of my games.