You're assuming he's using high-level inputs. If you have a sub-out, you don't even need to run the speakers through the sub.ice, you've got a pm sir.
It would go like this...
source device (cd player, tv, mp3 player, dvd)---->receiver---->*sub/plateamp*----->mains
*If you have a sub setup
The receiver is the amp.
You don't need a preamp for what your running, If you run individualized pieces, you need a preamp, but if your using a receiver, you don't need one.