Heat sink paste is a must with todays high performance, power gobbling CPUs. However, the stuff that comes on the heat sinks is junk. Scrape it off and buy yourself some good heat sink paste (also called thermal grease) from Radio Shack. It costs about $2. If you want to drop the cash, then spend $10 and get a tube of "Arctic Silver II". It is supposed to be a special heat sink paste that contains actual silver to help with heat transfer. After actual hands-on testing, I've personally come to the conclusion it isn't worth the money, and plain old white thermal grease is fine, but YMMV.
I've been overclocking systems for quite a while and I was water cooling back in the day before water cooling became the "in-thing". I've also played with peltier coolers and several other off-the-wall cooling techniques. I don't mess with it anymore because the CPUs available today are plenty powerful and are capable of far more than the entire rest of your components combined. Overclocking was the cool thing to do not too long ago, but CPU power is no longer an issue really. Your memory and busses are now the bottlenecks, but I suspect that once again, someday, overclocking a CPU will come into fashion again as bandwidths are increased and memory speeds go up...it's a cyclic thing. CPUs are on top now and the rest of the parts have to play catch up.....but they will, of that I am certain.
