I'm planning to build a new rig a little later this spring. I'm definitely going the AMD 64-bit route, but I haven't found much information on the difference between the AMD FX series and the "plain" A64's. Is there anything that great about the FX chips to justify their considerable additional cost?Also, I'm assuming that Socket 939 is preferred these days since it should have more longevity than Socket 754. True?

I'd go with a S939 Athlon64. The FX is a little faster due to more cache and sometimes higher clockspeed but it's too expensive to justify the small speed increase.

There is other differences. Now I don

Also the FX line doesn't feature Cool n Quiet technology. Not sure how important this feature is to you but I love it because it makes the CPU fan nearly silent when just browsing or doing other basic things that don't need alot of CPU.

Just looking at prices at NewEgg, it looks like the A64 3800+ is at the sweet spot of price vs. performance.Quick question on Cool 'n Quiet technology - will it work with any Socket 939 HSF? The AMD website mentions that the fan needs some kind of temperature sensing to work with it. The HSF in the retail processor package is supposed to be compatible with Cool 'n Quiet.