This is a fairly comprehensive look at 64 bit processing, however it's kinda old and therefore won't include a lot of the new stuff that's availible on the market today.
Basically you're looking for a socket 939 processor and motherboard. The Venice most probably will prove to be better of the AMD cores, however it's really only beneficial if you plan to overclock it. Otherwise, a Winchester or Newcastle core is fine, Winchester if you're concerned about heat, and Newcastle if want a bit more punch to your performance.
sorry i pm you gaara but what is this new core going to do. i would like to oc but i also need to know what to site it on and what to use for cooling for this 64. i have a xp so this is new to me alot on 64 processer.
well obviously water and air would be two completely different things. Water is always better than air with the exception of buying a crappy kit compared to a top knotch air solution.
of course the BEST cooling would be phase change But I know that aint gonna happen.