nice setup, probably better than mine actually:
AMD 64 4000+ (San Diego)
DFI Lanparty nf4-dr mobo
1gig corsair memory (2*512mb)
Geforce 7800 GT
hiper 580W PSU
I'll tell you from the research I did beforehand, that the 4000+ scores a lot higher on the benchmarks (for gaming etc) than ANY of the dual cores and especially than the equivelant ones in rating (i.e 4000+x2) because they are scored in capability rather than speed (afaik). The 4000+ san diego was placed very high on the benchmarks that mattered to me...
eg:
http://www.tomshardware.com/2005/11/...05/page24.html
I have to say its not dissapointed me, and i've managed to overclock it to 2.64mhz, as oppose to 2.4, without putting the voltage up so I could probably go higher.... so... if you are looking for brute force, I would recommend that, of the two...
Bear in mind though, that when the revolution comes (i.e when vista and the like, and the games that begin to really use the power of dual cores.. they will take over, and so its more of a long term investment...)
If you are looking for a one time investment, I would probably go dual core, but I think its going to be a couple of years at least before the dual cores will start to catch up, and i am hoping to have more money to burn by then
.