Unlocked cores on amds always run a chance of being unstable. I've heard that quite a few of the 3-core processors that are unlocked have problems such as the core running at lower clock speeds and stuff. You might have just gotten bad cores =/
A lot of viruses/malware aren't detected by any antivirus programs. Go to start>run>type 'msconfig'>Go to the startup tab. Look for any programs that look suspisious, names such as DdsCtdE.exe are usually viruses. Just uncheck any that look like this and restart, see if that helps.
If you're worried about the noise, I'd definitely invest in a fan controller. It will help much more than new fans and will last you forever. This one is noted as very good by almost everyone, and its cheap
Scythe KQ01-BK-3.5 "KAZE Q" Fan Controller
I like these fans also:
You'll be fine for now, but I wouldn't recommend buying a GTX 570 unless you're planning on upgrading your cpu =/ Your current one will bottleneck your framerate if you're playing on high settings/resolution. Probably should think about moving to an i3 or a Q9550 or something similar!
Ram speeds above 1000mhz have been shown to show almost no performance boost besides memory benchmarks, and the same goes with timing (cas latency). Voltage can easily go to 1.40v without harming anything, as long as the temps aren't too crazy. I've heard that you should try to keep it under...