Building a Linux Cluster

I want to maximize my parallel CPU power for my budget.

I've worked up this node configuration:

Processor: AMD Athlon XP2400 $72.99
Motherboard: Biostar M7VKQ-Pro $46.99
Memory: K-Byte 256Mb PC2100 DDR $49.99
Hard Drive: Seagate 40Gb 7200 $59.99
Case: Antec Minuet Slimline 220W PS $61.99
CPU fan: Low Profile Copper Cooler $18.00
Case fan: Sunon 40x40x10mm slim $6.99

Total: $316.94

I was thinking that 3Ghz intel CPU/boards cost twice as much with only a 20% gain in CPU speed -- with these 2.4Ghz Athlons I can increase our total CPU work/time by 60% for the same amount of money. (Then I found out about hyperthreading, so that confused me some more.)

Do you think 220W is enough -- the CPU will have to run 99.9% for days-weeks-months at a time but there are no cards or disk drives to draw other power (the motherboard is microATX and has onboard video and ethernet -- after installing linux I can transfer files by front USB key or local eithernet).

Would rackmount boards be better? I've never even seen one.
How would you build a cluster if it were up to you?

I think all the websites for these components are directron.com, tigerdirect.com and frozencpu.com.

 

I found this power supply calculator that is very useful.
http://www.jscustompcs.com/power_supply/