Summary: I am not a Bose hater. I have a few of their items. However I ordered both the Free Space 51s and the Definitive Technology AW6500. There is a stunning difference in performance between the two pairs of speakers. The Bose do provide a sound that seems to surround the listener. However the Def Tech's are amazing. The base is solid, not mushy and the fact that the Def Tech's have a midrange and a tweeter just blow the Bose away.
Summary: I have been running my 51s for a couple of years now. At low volume levels they sound nice, but their bass is very limited and I have found that they begin to distort at very low volume levels. I am running 100 watts RMS to them through a Sony ES receiver, so the source should not be the problem. I recently bought a pair of the Mirage Omni 6s from Crutchfield to support the overworked 51s and mounted them under my cover lanai with the Bose out in the landscaping.