You may want to do a "search" for Emotiva, lots of discussions through the years. Personally, I had bad luck with their MPS-1 shutting down all the time with my m80's. Some others have had the same issues with the XPA series, some have not.

Any receiver and/or amp can drive speakers of different ohm ratings at the same time, you don't change some setting to 4 ohms. That being said, make sure you use a reputable brand AVR that has been proven to not have issues with driving 4 ohms speakers.

Still not sure why you think you need an amp.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85