I am not familiar with the SMGa, but I have driven the MMG's with my PS Audio 100 Delta amp, rated at 200W into 4 ohms and had great sound. I also drove them with a Hafler 9130 rated at 75W into 4 ohms -- and a lot less current -- and had satisfactory sound. Decent amps with adequate current?? I would think Parasound, Bryston, and PS Audio--if you can find one. The Parasounds are probably the most economical/readily available.
Good luck!
Good luck!