You said that a sub would help in the lower end, however, both the EP175 and EP350 go only just slightly lower than the M60's. So how much of an improvement would I really notice?
I remember a couple years ago when I had a center, two floor speakers and two surrounds... the floor speakers shook the room on my HT system. Then I changed and replaced the floor standing and surrounds with four bookshelf speakers- and realized quickly that I needed a sub- and it definitely added the kick to the HT, but music with a sub just plain sucks. I would hate to have to go through the trouble of turning the sub on/off each time I switched between music and HT... so I figured the M60's alone would solve my problem..
