The 600 is smoother than the 500. If music listening was important to you, I’d say go for the 600. But seeing how this is a dedicated HT, the 500 would be OK. But, most movie sound tracks have a lot of music, so that’s your call…..If I were shopping for subs again; I’d opt for two 500’s.

The M60’s should also be just fine for a HT. The 80’s play a little lower, but you’ve got the sub. Again, for music, I’d go for the 80’s. For strictly HT, I’d go with the 60’s.