I'm wondering if the receiver line out's to the M3's is faulty. I know I have an older Kenwood receiver with an A/B speaker function and the "B" is broke.

Jerry, just to rule this possibility out, can you swap the M3's to the other output? If nothing changes, then a call to Axiom is in order. You should not have to crank the volume much to level match the M3's to your Cambridge speakers.