machine specs

Hello,

i'm deploying a 2 new servers at our school
1 TS 2008
1 DC 2008
there are +/- 200WS and we ahve remote users for the TS

I'm going to install a Forefront server for the internetconenction &
security. it need not to do anything then that.

I don't have the slightest idea if this needs to be a very powerfull
machine or not.
Wich are the spec's on the machine that I will going to need
64bit and....

tx for the advice