7.1 is overkill for anything but a very large living room. You'll be safe with 5.1.
Most last-gen games (and Wii games this gen) support Dolby Pro Logic II, which is basically simulated surround sound. Xbox 360, PS3, and certain Xbox games support true Dolby Digital surround sound. Either way, it's very much worth it as a gamer to invest in a surround sound setup. Just make sure your receiver supports multiple digital audio connections.
"'Casual games' are something the 'Game Industry' invented to explain away the Wii success instead of actually listening or looking at what Nintendo did. There is no 'casual strategy' from Nintendo. 'Accessible strategy', yes, but ‘casual gamers’ is just the 'Game Industry''s polite way of saying what they feel: 'retarded gamers'."
-Sean Malstrom
