Well afterall you may not need 4 gigs in that case. You plan on running Vista? This can be another reason to get some more memory.
4gbs is overkill and you wont even utilize it all without a 64bit OS.
Also chipset has absolutley no affect on the gaming fps if you are not overclocking. After countless tests improvments between different chipset is minimal at best, and that is only after heavy oc'ing
that said p35 or x38 chipset gets my vote for future proof, and drop the extra RAM so you can spend more money on important things, like GPU/PSU/CPU