Well, when multi-threaded games come out, there will be no contest. The dual cores will win.
However, I found some benchmarks on tomshardware. And, there was like 1 fps difference for the 4000+ on two different benchmarks. One had the Newcastle 3400+ 2.4 GHz socket 754 CPU on it and the other one, an X2 3800+. The socket 754 chip had something like 151 fps in UT2004 while the X2 3800+ had 136 fps.
Heh, I found the 3400+ 2.4 GHz on sale at Compuvest for $163 US. Even with the $25 shipping to Canada, it was worth it (even with the duty).
In two years, I"ll just build a dual core machine. I suspect many things will be different by then (SATA2, PCI-E2, DDR2, high definition DVD or Blue Ray discs etc...)
\EDIT: I just found those links.
http://www.tomshardware.com/cpu/200508011/athlon_64_x2_3800-07.html#directx_8
http://www23.tomshardware.com/index.html?modelx=33&model1=64&model2=18&chart=27
You can look at the test set ups as well. They both used a 6800 GT. There are small differences like RAM timings and motherboard chipsets but, about the same with fairly similar results.
This proves the 3400+ 2.4 GHz is a pretty good deal for the price.
