I'll toss my agreement in
Dual CPUs are nearly uselss for games.
AFAIK the only game that really uses multiple CPUs is Quake3..and it's graphics engine is single threaded...so your 2nd cpu can do sound and network? Keyboard polling? Not much...
There are lots of good reaons to use dual CPUs, but for games 1 faster one is better. Get a 1Ghz P3 and an i815E