Basically I bought an off the shelf Synergy from DVillage...12Gig ram and two 350Gig drives. The thing runs very very quiet. Total cost was about 1500 sterling but I already had XP64 so that's not including the OS. I'm sure you can do it much cheaper (and much more expensive) but the Synergy seems good value considering it fits into my rack and doesn't make any noise.
This will all seem like exceptional value once VEPro arrives... my macbookpro will probably be asked to work another three years!