In my small living room (12x10), I'm starting to think that I need a little more depth to my sound. I have bookshelves (bostons, cr-6) and am considering getting a sub, but is that a good setup for music? Subs seem popular for HT setups, but not sure if I should get the sub for music primarily or instead invest in a new set of mains w/ more bass. Any suggestions? Thanks!