I'm still think that the 64 bit technology is not consolidated yet, but you'll be ready for the future O.S and i believe with this machine you'll not have to change it for 2 or 3 years. Unless they release something so new what you have to get one of it.
SCSI - RAID 5 - a very good dream.
Go on man, and buy your new pc, i'm started to think about to buy a new pc too, but here is too expensive, do this to you have an idea of the price here.
Do this calcule: ( your total price * 2,90 + 20%(store taxes) = my money to spend).