80% music, why would you want rears?
Listening to music in anything other than 2.0 or 2.1 is just an inferior music listening experience. Unless you use formats like SACD which went nowhere, music is not even engineered for 5.1, so all you are hearing is artificial.. mere simulation of surround sound and emulation. If you really want the best music experience and want the most accurate reproduction of the artist's recordings, get 2x studio monitors from brands like Paradigm or B&W, and a solid woofer if you're a bass oriented kinda guy.
What sucks is when you listen at Best Buy, they never have anything near its full potential. Nothing will be eq'd at all, they'll demo music for you on low end ipods , won't understand when and where to connect analog or digital, etc .. that's if you're lucky enough for them to figure out how to set everything up at all.
How far away is your nearest mom and pop shop that would carry brands like Paradigm, B&W, McIntosh?