Welcome Mountain,
First of all, you should never adjust the ohm setting on a receiver, as that just limits the voltage, providing less power to the speaker. The 8ohm standard selection will work fine for most situations.
All I can tell you is I found the m60's and m80's similar to the B&W 703's about 5-6 yrs ago. As you can tell, I'm still an Axiom owner.
I've also heard the Axiom lineup is similar to the Studio series from Paradigm.
The m60's and m80's are a great all around performer. They have great detail and accuracy, and good/tight bass response. The m80's can handle more power, and might be slightly better in the detail/bass categories, but it is very close, in my opinion haveing owned both.
I've always told people the M60's/M80's are very true/faithful to the original recording/CD. Music that is recorded with the best engineering techniques in the studio, will sound fabulous. On the other hand, if your listening to compressed mp3's, or CD's recorded with sub-standard quality, those flaws might be heard. That is not the problem of the speaker, as some may tell you.
Any receiver should be able to drive a 4ohm speaker, the receiver doesn't know what is on the other end. However, if you really push certain receivers to loud levels for a long time, some may go into protect mode and shut down. Denon's, HK, NAD, SN, Outlaw Audio, etc. have historically been recommended by Axiom. In the past some Yammys and Onkyos have had issues, but I've heard the latest models are more compatible.
