My short advice, which I stumbled over by accident, is to look for something QUIET. You don't really need any more horsepower, though some would be nice, but having a QUIET machine can make a phenomenal difference!

I got an Intel motherboard and P4-2.4GHz CPU -- the fan on that CPU is much larger and quieter than on any previous CPU I've owned, and really suprised me. And I had to upgrade the PSU to handle the 6-drive RAID I was working on at the time, so I got an Enermax quiet supply (lots of other brands out there too), and the combination was really impressive. Six IBM deskstar drives in that box, and it was nearly whisper quiet!

The RAID is now in a different box for SMP testing, and so there's now just a single Maxtor 160GB hard disk left, and is really is no noisier to use than my laptop now. Sure the laptop is quieter, but the fan on it is much closer to my ears than the box under the table is.

I haven't yet bothered teaching RedHat9 about ACPI suspend/resume, but this box is fully capable of it -- works with win98 anyhow.

So.. in summary, think (hard!) about noise levels!

Also, your next MB/CPU may REQUIRE a new power supply -- the P4's do, dunno about the latest Athons.

Cheers