I have a P4 2.4GHz Prescott and I bet Quake Wars won’t run very well on it, although I can play Doom 3 at near high settings with only an occasional stutter.
It’s a hard time to upgrade, with Vista, DX10, and the new generation of video cards around the corner. I priced a nice E6400 dual core and a mobo at NewEgg the other day for around $320 which isn’t too bad assuming you have the other hardware to complete a new PC with. I’m near to my time of getting a new PC, and expect to put out between $500-$1000 for a new system before Quake Wars comes out. Thats just mobo, cpu, mem, hdd, and probably a new psu.