To add on to what John said, you could also start with the Denon S670, upgrade the towers to the T5's (extra $30 each), get the center C5, and start with a nice 3.0 system (the T5's, which I own, have very good bass response) for under $900 not including cables, then add-on a sub and surrounds...
If you change your mind and decide to go with a receiver, here are my recommendations:
Option 1:
Denon AVR-S570BT 5.2 Receiver: $309.99
Monolith Audition T4 Tower Speaker ($99.99 ea x 2): $199.98 pr
Monolith Encore C5 Center Speaker: $74.99
Monolith Audition B4 Bookshelf Speaker ($49.99 ea x...