It's still the GPU holding him back though. A now cheap 9800 Pro would literally more than quadruple his FPS (almost three times the bandwidth + double pipes) and have DX9 features + better anti-aliasing quality, while an upgrade from a 2400+ to a 2600+ (what he is suggesting) is hardly going to make any difference, and that upgrade would be a waste of cash in my opinion.
When building a system, you should try to find the weakness and balance your system. It's no use having one component much faster than the others, since it will hold you back and your FPS will suffer. I second the Athlon64 opinion, although in his case he already has a fast enough processor while his other components are much worse.
The motherboard option is marginally better than the Via, but not by all that much. Might as well save up the money and get the Slot 939 system that you really want, RJARRRPCGP, and start afresh, and sell your old system to raise the funds (this is what I do).