I've been playing around with overclocking it the last few days, and currently have it at 4.2GHz, up from stock @ 3.6GHz, and bumped the GPU clock on my GT 640 from 902MHz to 997MHz to get a little more juice out of it... mainly just because I can
. Everything seems to be running stable so far. I also ditched the stock CPU cooler today and put my Coolermaster 212 EVO on, and have been quite happy with the temperatures. I really need to get some more (faster) RAM in it, but have been trying to find a good deal. I currently only have 4GB of DDR3 @ 1333MHz.
Overall, I've spent a total of $41.85 on this computer out of my own pocket ($20 for the CPU, $21.85 for the fan), not counting the parts I already had, so I'm pretty happy with the results lol.