Hello everyone,
I've been using a set of M80's for about 2 years now with a 15 year old Luxman integrated amp. It is rated at 70w/ch at 8ohms. It is a super clean amp that sounds terrific. On the back of the unit it states that it wants 8 to 16 ohm speakers.
The only time I have a problem is when I am listening for extended periods at extremely loud levels. The amp will start to get hot and then go into thermal shutdown. Within 2 minutes, it has cooled sufficiently to come back on. (Usually this only happens when I have had too many beers)
Don't forget that the 80's are very efficient with the power delivered to them, so they play loud even at lower volume settings. Most people I have over can't beleive that the amp is only 70watts.
Don't be afraid of the 4ohm rating unless you are looking at very inexpensive receivers. Most NAD, Denon, and H/K units should handle the M80's with no problem.
