It's Time to Build a New Computer
I'm almost definitely going with a Core 2 Duo E6600: it's the optimal point on the diminishing returns per dollar spent scale. Everything else is up in the air. 2x1GB DDR-800 RAM seems the way to go, and I can always add another 2x1GB in the future if necessary.
I'm probably sticking with a GeForce 7 series for cheapness (it'll be more than enough to play HL2 and most of the other games I've missed). I'll upgrade that later, likely immediately after nVidia announces their next product line. Videocards have changed quite a bit, so I have to dig around for some solid benchmark comparisons.
I'm leaning toward the Abit AB9 motherboard, though I'm leery of leaving behind the nForce northbridge I've always been so fond of. It doesn't look like it matters, however, unless I want to stupidly do SLI, which I don't. If I get that motherboard, with its ludicrous number of SATA ports, I'll probably run my OSs on either a single 400GB drive or a pair of 200GB RAID 1. I'll fill the rest with 400GB in a RAID-5 and make the box my personal datastore.
I still have to do a lot of research on soundcards. I have a perfectly servicable Soundblaster, but I really want a professional card. The sticking point isn't price, but functionality in Linux.
I'd post my beta Newegg wishlist, but my work blocks Newegg for some reason. Have to get that up when I get home.