Dear SJM as both Fred and Socketman have said go big or get stuck with the upgraditis bug. I as well suffer from not enough subwooferage.
For just classic rock, Pop music, soft rock and that kind of listening your M60 Vp160 combo will be awesome. If you like classical, Jazz, newer pop music and movies you'll want at least the EP500.
The D.S.P. in the EP500 is for its own tunings control, to benefit your Audessey or A.R.C. MINIDSP etc. So that what ever frequencies it reads doesn't deviate to much. Only 1.5 Db range from it's signal.
The MiniDSP is regarded as the best on the market right now, but you have to get one of the UMIK or similar to use it.
As Socketman said go slow and find your needs or wants first, Though beware don't jump in with a small sub that only goes a little lower than your towers. As most of us ADD more subs or go bigger, then realize we should have just done the big lower frequency one in the first place.
