Here's what I'm dealing with:
366 Celeron
192 Mb RAM
ATI Radeon 7000 (32Mb graphics)
40G hard drive
DirectX 8.1 presently (will upgrade to 9.0 of course)
I'd be a little concerned with the CPU. It still needs to be fast enough to transfer data to the other devices, regardless of how much extra load they can handle. But you really can't tell until you try. Until I could afford otherwise, I was very used to playing games on underpowered machines.