The fastest drives I know of right now are the WD Raptors, 10K RPM SATA drives. The 74 Gb has a 4.5 ms seek time, the 36.7 Gb has a 5.3 ms seek time. (That can make a difference sometimes) They both push 150 MB per second.
I run 2 of the 36.7 raptors in my tower PC, raid 1, with 1 Gb of DDR 400 RAM, and and AMD 3000+ 400 FSB CPU. (Socket A)
That thing is very fast...
Your machine would be even faster than mine with that 64 bit CPU and (2) 74 Gb raptors in there on raid 1 (mirrored) array.
Go for a Gig of RAM, it is cheap enough and well worth it in a PC like you have.
BTW, that board you have is awesome,..great choice.