Use multi-CPUs from the go. Upgrading single to multi has never worked well from MS. Leave yourself room to grow, so buy a 4, 8, or bigger box and start with 2 CPUs.
RAM - as much as you can afford. 1GB prob a good min these days with prices low, go for 2 if you can.
As many spindles as you can. A big array like an EMC is nice if you have the $$, but may be overkill. Personally I recommend having at least 3 (preferebly 4) physical arrays. I say arrays becuase you want to spread the load. Also, buy "smaller" drives and more of them. 4 9GBs work better than 1 36GB in general.
Array 1 - Raid 1 - W2K OS, SQL System files, backups can go here.
Array 2 - RAID 5 - Data files, nice to have one of these per user database, but at least have one and as many spindles as you can.
Array 3 - RAID 1 - log files. Again, nice to have 1 per heavily loaded db. The reason: log writes are sequential, not random, so it's nice to have the drive heads relatively stable.
Array 4 - If you can, drop the windows pagefile here. Again, backups and misc can go here.
Network - At least 2 NICs. Keep one for fault tolerance. You can always have separate IPs for each and use one for backups, management, etc. and one for the workload. If it fails (not likely, but it happens), then you can switch the other over. BTW, use 2 different hubs if you can for these 2.
at least 2 power supplies. Each should run to a different circuit (through a UPS).
Remote card is nice
Have enough backup capacity. Local tape backup is a bad idea, IMHO, but be sure you plan for backups somehwere.
Test system - leave enough $$ for a test system that can be restored from a copy of the live system.
BTW, if you are building a workhouse, build a SQL 2K workhorse and run it in 7.0 mode if you have to. Lots of enhancements to query engine, backup engine, etc. in 2000.