Quake server SMP only? That stinks.
I am running a pair of 1 gig P3's on a MBI motherboard I picked up at CompUSA recently(VIA 694X + 686B chipset). Amazing, I was able to swap it in in place of a Soyo motherboard with a VIA chipset without having to reinstall the operating systems. Nothing is overclocked due to I have cheap ram that doesn't hold well above 135 mhz, but there's 768 megs of it. Eventually, I will splurge for quicker ram, maybe 150 mhz with quicker timing.
As for the rest of the system, I use a Tekram Ultra 160 dual channel scsi controller with a pair of Quantum Atlas 34 gig 10k2's. Thinking of dropping in an old 4.3 gig IBM ultra wide drive for on-the-fly back-up of important files. Other cards include Pinnacle DV500 capture card, Hollywood DVD playback card, Elsa Gladia GeForce 2 GTS(32mb), and a lowly Soundblaster PCI 64. Other drives are a Pioneer DVD, Teak 4x24 CD-R, LS120 ide, and ZIP250 ide.
By the way, since you're big on smp, I also have an old BP-6 with dual 500mhz celerons overclocked to 566mhz.