Any THX Ultra receiver is rated to be able to drive 4 ohm loads continously. I would recommend the 60's for a different reason. Having had both (now running the 60's), the M80's are much tougher to place and are considerably more picky to placement to get the proper soundstage. You need to be sitting at around 15' back to get the proper stereo imaging from them. They also need to be further away from the wall as they need more room to breathe. The M60's are more forgiving than the 80's as far as placement is concerned. I didn't feel the difference was enough to justify the price upgrade between the 60's and 80's. The 60's did everything I needed them to do without breaking a sweat. I would take the money you save and either buy a better receiver or invest in room treatments or a hi def player.