Re: Trying to find a CPU Upgrade
according to your specs your upgrade capabilities are the 64 or 64 FX processors. You could take a decent upgrade to a 2.8ghz in the 4000+ or get one of the FX processors some of which I've seen out perform or as well as dual cores.
Thing about the FX series, is based on what you're using it for. In my personal experience, my single core AMD 4000+ @ 2.5ghz(i think) was good for what I needed it for and certainly a jump in performance. I use to run a P4 and 512MB of ram also.
In regards to heatsinks, it's based on your current heat on the processor or the one your going to upgrade too. Stock fans do a pretty good job of keeping your processor cool, but I think thermaltake would be a pretty good choice.
i5 2400 @ 3.10Ghz | 16GB RAM | 500GB + 1TB | GTX 750Ti