I would have to say..

If your just modeling:

A quad core with 4gb of RAM, with a good VC.. such as a quadro.. <-- read into them and figure out which one u want. like.. are you a professional.. intermediate.. etc.. that deteremines ur card and price.. only u know the answer..

some folks are all uptight on hard drives.. a few miliseconds to me here and there are not that big of a deal.. But if your up to it.. set up some SAS drives in RAID 0 .

for storage get a flash drive.. simpler.. easier.. and no need for redundancy..

for rendering

the biggest fastest core you can afford a minimal of 6 gbs of ram, same with the VC.. same with HDD's