Magnepan MMG for HT

I think you're changing too many variables all at once. You won't know what does what in your system, by changing the processor and the speakers. I say change the processor, and upgrade to the latest Digital. Dynamics and detail will be a huge boost with this upgrade alone!
Also, are you running your speakers crossed over as small or 80hz? You should be! Dynamics will greatly improve. making sure speakers are placed properly, and sub properly integrated and placed.
Another benefit of later processers here, is that you can likely get state of the art room EQ, which also helps tremendously.
Yeah, work on the processor, settings, and setup you have now (tweek it), and maximize the foundation of your existing tools.
Fer the record, the Maggies will offer you a small sweetspot for one or two listeners, with their dipole configuration and WAY cocused soundfield, and aren't strong in the macro dynamics department. Otherwise, they offer a very detailed, clear, and uncolored sound - but they are on the delicate side.
Basically, you watch Iron Man on the system, and things don't offer the level of impact and strength of piston speaker systems - all things equal.
Later, you can move onto more efficient ht dedicated speakers, and see what real dynamics are for maximum HT nicesties.

What sub intergates well Maggie mmg, two channel set up.

I started my HT system with B&W 602's for the front, 601's for the rear, CC6 for the center, and a Velodyne sub. I then replaced the 602's with MMG's with very good effect. Now I have the MMG's in a two channel only system and the 602's back in the HT system.

Maggies are notoriously ineffecient so be sure you have plenty of power for them and they are harder to place than the 602's you have. In terms of wife approval rating, the 602's are a better choice. Otherwise, say sound great.

Forgot to mention that I have a Velodyne sub. Does your friend use the MMG's for all 5 speakers?

There is much bass/ full range info. on 5.1(to the rears) Unless you sub woof,you'll miss a lot.Have a friend who has them in a great room,but he sub woofs with great results.