I'm too a classical fan, and also have M60's. I'm basically going to repeat what others have said, in that Axioms, like most mid-high end speakers, make great recordings sound as they should, and not as friendly on poor recordings. I have two Ep500's, and ALWAYS have them on for classical material. My reasoning for this is that most classical pieces(that I have anyhow) are usually lacking in the lower regions, and the 500's add a subtle weight to the music that sounds great. But with more bass intensive music, I tend to leave the subs off, as the M60's can go down deeply and cleanly. As for the EP175, I can't really comment on it, and you'll find that there is little to no literature on it online.
For the center channel, I originally had a vp100 and wasn't very happy with it, I wasn't used to it's flat, natural sound and I sent it back for the vp150. The vp150 doesn't sound much different than the 100, but I have grown accustomed to it's sound and rather enjoy it now, but I have to admit I wish there was something a little better in the Axiom line for centers.
As a side note, you didn't mention what you were using to power the speakers. I orignally had a Yamaha v2600 powering 7 channels, and was somewhat dissapointed. I looked into seperate amplification and purchased an Emotiva LPA-1($499) to power 5 channels and was extremely happy with the performance it gave me over the yammie. I was so happy with Emotiva's entry level amp that I returned it and purchased two of their 2 channel behemoths RPA-1(200wpc x 2!) and it's absolutely blown me away so far. I've only had them for a couple days but these things are keepers. Movies and music have never sounded this good before and I'm convinced that seperate amps are the way to go. I listened to The Miraculous Mandarin yesterday on SACD and was astounded by the sound reproduction, if only the music was good I may have had an eargasm.
