I must say this now, despite what my father said about custom built PC's having issues out the ass, I have got quite a stable system (though I learned that Nvidia drivers, PARTICULARLY with the GTX 560 and 560 ti, don't like Firefox+Hardware Acceleration).
However, I will say this...I won't try overclocking my GPU's anytime soon. I tried that once for excrements and giggles, but my system HATED it. I would get bluescreens out the ass from doing it, and promptly downclocked back to factory and system restored to wipe any trace that I did it from my computer. It stopped immediately. If I do upgrade my computer's graphics performance, safe to say, I'm just gonna get a better card. The money, from THAT experience, tells me it's worth plunking down cash. Especially since I could just sell my old cards for like, 150 each on eBay, which is 110 less than I bought them for anyway...nyeh.