I think 13.1 is something the studios will use for movie theaters. Comercially it makes perfect sense to have 13 independent channels. Just think of the possibilities in a room so large. I think you guys are right for the home though. 7 is plenty.
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Family room
Outlaw 990/7125
Klipsch RF-25's, Klipsch RC-25, Klipsch RS-25, Klipsch RS-52's

Home theater
990/7125 - Until the 978 is released
Seymour Av xd 120" screen
panasonic pt-ae7000u
3 In cabinet Axiom M80's, 4 Qs8's, In cabinet EP-800 subwoofer