I also have a 4311 with M80s and a VP150. I use a 3ch ADA1000 for the fronts. I definitely hear a difference and just love how it all sounds. My room is about 2600 sq ft and it can get pretty loud but I wish I would have a bought a 1250 instead. I will probably upgrade down the road.

Main points:
- I play my M80s in full range (Large) and my Denon would shutdown with some movies (Tron Legacy for one).
- Music sounds so much better with the ADA. I play music as 2.1. The M80s really shine and to my ears is a pretty big improvement over the Denon alone.
- When I watch action movies and have the volume turned up, the external amp really makes a difference.
For every expert, there is an equal and opposite expert.