For audio only, I have ended up with 2 X M2s plus 2 X EP-400s. This little system is stunningly musical that brings me more pleasure than any gear that I've owned in my 40 year journey through this pastime...
Tam. I was incredible impressed by the treble and mid range in the M2 when I tested mine in 2.0, but found they were obviously lacking in bass. I'd love to compare them, paired with a sub, to the M60. I bet they would sound very close if not every bit as good as the M60.
To the OP, I was surprised at the bass output of the EP-400 when I listened to it. Unless you are listening to pipe organ music or something else with content down to 20Hz that the EP-400 would do very well.
Ask the folks at Axiom. They will not over sell you.