I think this topic actualy has come up often, you might want to try using the search option and I bet you would find good feedback. I can't help, never heard Ascends...
Hi there! Not too long ago, I posted my own personal comparison of the classic CBM-170's and the M22's here. I could have done a more thorough comparison if I wanted to, but just trying to gather up those thoughts was enough to drive me bonkers! Anyway, I hope it helps! I really wish I could get a chance to listen to the 340's as well.
A couple of us got together a few years back to do a comparision. If I recall, ascend was a little fuller, and Axiom had more detail. Both were good and I think we all would have been happy with either. I'm sure you can dig up the thread with a search.