To clear up some statements:
a) The Athlon 64 X2 will be 2x2.2 / 2x2.4GHz so not much clocked below the FX series
b) Best would be to have asynchronous CPUs, say 1 core runs with 2.4GHz the other one with 1.2GHz, because for most uses, we'll use 100% of one core (say: gaming) and the lower clocked core would handle, say winamp and all those other tasks running in background.
c) SLI suffers the same problem, ATI addresses is by enabling to run 1 high end GPU with 1 lower end. ATI SLI (called AMR) isn't final yet, though, things might still change.
d) Win Server 2003 is patchable to support 64 bit
e) The new GPU gen will be out due sommer, featuring R520 + co and will give you an up to 100% speed boost again.