Hi aerial. Others will be along at some point that can give you really good advice. I have had the M80s for about a year and a half. Started with the vp150 and upgraded to the VP180. Others will be able to give a better evaluation but I will give you the best description I can. The speakers are really amazing. The M80s can play really loud and yet so clear. When I have friends or family over they are so amazed at the detail. My son-in-law has a decent HT set up and loves the clarity and detail of the M80s.
The VP180 makes the dialogue in movies jump out at you. My wife is 75 percent deaf and loves the 180 because the voices are so focused and sound like the are just right there.
I assume on the Onkyo you meant the 5008. I have the 3007 and it will push the Axioms as loud as I can stand to listen. So I think you would be very pleased with that setup.
Hope this helps.
This is a great place for good info. And there are some guys on here that can really give you some better discriptions than I can. So I am sure you will get some more good advice.
Welcome and enjoy.