I really hate to recommend people a product that I have because it seems like that is all anybody ever does on forums, But for 5k, personally I would check into some stratos mono extreme's .
I haven't heard the Odyssey name in awhile but Klaus? used to get one heckuva reputation for customer service.
Built simple solid amps.
I also do agree with other comments that it is a little skewed to spend 5k on amplification for the M80's when you could spend 5k on speakers and 1.5k on amplification and get a better setup overall.
For 5k you can get a larger speaker (or more speakers), maybe fancier finishes and for under 2k you can get a TON of good amp options.A TON!!