I would recommend buying in this way, if you don't want to buy everything at one time
1st: Mains. Pair of M22s, M50s, or M60s.
2nd: Surrounds: pair of QS4s or QS8s. (You don't want just one surround. You can buy them that way, but generally that's considered an option so you can go 6.1)
3rd: Center. Either a VP100 or VP150, depending on room size.
The sub should come somewhere around 1 or 2. I'd be looking at 350s and up.
I own a modified Epic 50 (without the sub). Axiom is willing to sell you whatever you want. 5 or more items in one order gets the 5% discount that the prebuilt systems (the Epics) have.
As for the surrounds, the current Dolby, DTS, and THX standards call for them to be mounted on the side walls, in the arc from slightly ahead of to behind the listening position, and 1-6 ft above the listener's head (I think that's the correct number).
