I'm finally replacing my sound (and TV-HD upgrade) system. I anticipate about 70% music, 30% home theater. I'm thinking of going with the M60's or M80. I'm not too much into the home theater experience but might occationally want to experience a bit of surround sound. Is it practicle to add just two rear speakers (for a total of 4)? Would I be missing any sound signals when watching DVD's or TV? I'm upgrading to a new receiver as well. Thanks.