I don't need a VERY large hardrive (the one I'm currently using has only about 23ish gig used up with all the games I play) and I found out my disc drive is become gimpy, haha.
I would recommend
this hard drive. I have that exact one, and it is extremely reliable. I've had no problems with it whatsoever, and 80 GB should be more than enough considering the amount that you've used thus far on your current HD.
As for the ram, I've heard about OCZ a little bit, is the overclocking potential worth the extra money? I'm have very little knowledge to overclocking RAM.
I purchased RAM called Corsair XMS, which is overclocking RAM, however I regret that decision because it is more expensive and I don't overclock. ValueRAM gets its name because it is meant to run at the rated speeds, no more. If you want to overclock the memory, you would have to buy the more expensive stuff. Personally, with the system you have, I would see no need to overclock your RAM or your CPU. Your CPU is very fast and can easily play any game you will throw at it. Also, overclocking the RAM leads to very neglible increases in speed, so I see no need for it. Of course you're free to make your own decision, that is just my two cents. If I was building a system all over again, I would buy
this RAM. It is cheap, only $108 for 1 GB, and you can run the two sticks in dual channel.
Not that sure about the SLI thing...sorry.
SLI is a technology that involves using two video cards on one motherboard, increasing graphics performance. However, it is INCREDIBLY expensive because you would need to buy two 6600GT's for example, instead of one. Currently, I consider it a waste of money because many games do not yet support SLI. Also, the 6600GT you have in mind will give you very nice performance.
And finally, what heatsinks, GPU fans, fans, etc. are reliable/efficent?
As far as the CPU goes, if you buy retail and it comes with a heatsink, you should be fine to use that one. The Winchester core runs very cool, and you should only need a new heatsink and fan if you're overclocking. As for the GPU, eVGA uses very good heatsinks on their video cards, and once again, you shouldn't need a new one unless you overclock.