Take my response with a grain of salt... I have not heard either M22s or M60s, or an EP500... but I'm ordering M60s plus and EP500 shortly (not to rub that in).
It sounds like you've already got a pretty solid grasp on the tradeoffs of either setup, and your personal preference for music perhaps goes a long way...
Everything I've read leads me to believe you would not be disappointed with the musical setup of the M22s + EP500. In fact, from everything I've read, it would be a great musical setup. Again, I'm only speaking after reading reviews, but the only knock on the M22s is that they lack bass... the EP500 clearly takes care of that.
Whether the M60s will help with "soundstage" or "depth"... I can't say. All I know is that it doesn't sound like you'd be disappointed with M22s and an EP500.
One factor that would tip it for me... the M22s and M60s are supposed to be "great" products. I've read a few reviews to make me believe the EP500 is an "astonishing" product. I'd go with the M22s + EP500, as you'd be getting your hands on what seems to be one of Axiom's most impressive products, the EP500.
However, if you go toward the M60s... Any chance you can fit a smaller sub in with the M60s? SVS' new "small" sub (SB12+) is intriguing... and I've read some great reviews on an even smaller, cheaper sub... the Onix Rocket ULW10 (12"x12"!, available for $400... see the review on Audioholics). Though certainly not an EP500, those subs could provide solid bass for HT.
Looking at non-outlet prices...
M22s + EP500 = $1660?
M60s = $960
M60s + SVS SB12-plus = 1660 (plus SVS shipping)
M60s + Onix ULW10 = 1360 (plus Onix shipping)
Anyway, my preference would be for a subwoofer. I don't think you'd be disappointed with the M22s + EP500.
