They are both different sounding speakers. The Def Techs are bipolar and the polks are direct. For music I would go polk but for movies I would go def tech.
I suggest checking out the Mythos line from Def tech if music is important in your system. Personally I don't like bi polar speakers for music but thats just me. The Mythos 1's would be a good speaker to put in your mix. I think that maybe the right choice.