Help me build a Theatre system for $5000

I'm just finishing my basement. The drywall goes up on Monday. The room is a 15'X 30' with a fireplace on one end and a kids play area on the other. Between is the HT area. So screen to couch is about 15'. So no real side walls but the couch is somewhat recessed in a 3' "bay-window" type area.

I live in a small town in Utah with VERY limited electronics selection. A radio-shack/hardware/plumbing/heating/candle emporium is my only local option.

What I have listened to (in the big city of Provo)and liked was an Onkyo 805 receiver with Polk RTiA9 fronts, CSiA6 center, FxiA4 surrounds. The only other speakers I had to listen to were Klipsch. I preferred the Polk over Klipsch. I have an RBH sub that I was going to use.

I am not opposed to used equipment, in fact that is preferred. I just need HDMI 1.3a to hook up a Panasonic 50" 1080p Plasma screen.

I'm just not name savvy enough to know what I'm looking for in this high end stuff. My current system is Advent speakers... bought in college and burned in with Boston played at 11. Thanks so much for any help you can be.

Stan