DescentBB

With a quad core cpu, will playing games like Oblivion make use of all 4 cores or only one? If only one then would it be better to buy a single core rated at a faster speed than what a single core on the quad die is?

Only if the game is programmed to run on multicore CPUs.

Yeah, I'm not sure about Oblivion, but some newer games are starting to be coded for multi-core processors.

That said, I've certainly noticed that having a quad-core machine still helps considerably even with older games like Descent3, especially when I'm running other things at the same time (Vortex, Ventrilo, etc.).

I don't think you can go wrong buying a quad core. Does what a dual core can and what a dual core can't.

Depends -- my 3GHz/1333FSB Dual Core runs the apps I mostly use faster than any Quad at the moment for < $200. Waiting for some decent Quads to show up for the next round of updates

Oblivion is NOT coded for more than one core. You will get no benefit whatsoever of a multicore CPU unless you are, say, running a 3dStudio Max rendering in the background in the other core.