Help me spec out my speaker system (with wiring)

[jc480]

Okay I have a room that I am setting up as a home theatre. The room's dimensions are as follows...

Depth - 25 feet
Width - 12 feet
Height - 10 feet

Setup: A speaker in each corner of the room mounted at ceiling level...wiring will run in the ceiling (access via attic)...I wish to run the wiring to the rear wall of the room (behind the walls)

A floor sub-woofer that "disperses" the sound throughout the room (sorry I don't know the correct term)

A "center channel" speaker that will sit underneath the 52" TV mounted on the back wall

A receiver -- thinking Yamaha? Do I want 5.1 or 7.1?

Lastly, do I want a pair of 3-4 foot stand-up speakers for either side of the center channel speaker or am I covered with the corner wall speakers?

Thanks...and yeah, I read the speaker 101 thread...I appreciate anyone who will take the time to give me some guidance.

- is Bestbuy a decent place to buy speakers? They seem to have knowledgeable staff...I have no idea if their pricing is competitive
- ancillary hardware...where do I want to buy cables, speaker wiring and do I buy this by the roll or ?