Mcintosh MA6500 4ohm Maggie or 8ohm Monitor Audio

New owner of a MA6500 integrated. Currently using a pair of Monitor Audio GR10's (8ohms 88 db efficiency) amp puts out 120 wpc. Thinking of going to a Magnepan MG12's. They are 4ohm with a 86 db sensitivity. The MA6500 will output
200 watts per channel. Will there be a significent difference in the addtional 80 wpc?
Which speaker system will match better with the MA6500?

Thanks for any input.
When I was at Lyrics HiFi in NYC with a friend, the dealer housed all the maggies in a separate room and they were only powered by Mcintosh Integrated. The dealer told us that maggie works very well with Mcintosh, that's why he paired them up to showcase what the maggies can do.