Don't forget conduit.
If your wall is now still open (i.e. "not yet dry-walled") now is the time. You can always add additional cable that you may not have thought of. Furthermore, your TV at other end of room may change. Might have high-def later on.
It's good to have options.
Also: the larger size, the better, the easier.
And always pull more than you think you need at this time. And always add a "pull-wire" [makes life easier].
Another idea: pre-wire it for phone. You never know.
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Living Room:
5.1 Surround and 4channel inline room
990/7700/6-KEF-107s/LFM1 x 2/ SMS Awaiting Trinnov
Millenium dts decoder;Digital Director
Players: Tascam CD01U/SonyCX455 x 3/DV955/BDP83
Old Sony 60" SXRD TV
Zone 2 (also liv-Room: listening to music while Mrs watches TV): Crown SL2 preamp/D40 Amp/Stax Headphones
My "Man-cave":
4 channel-only inline room. No TV (thank heaven)!!!
990/755/4-KEF 107s
Tascam CD01U/dts decoder/digital director
Alesis 16x4x2 mixer
Recorders Alesis HD24/ML9600/Crown CX844s/SonyDAT/Tascam DA38
Ham Radio Shack (KB1STH) ICOM/Yaesu/Drakes x 3