I have an AAC M4-2000 and it's one of the better suppressors that I have used. We were out again a few days ago shooting well into the evening. I am always amazed at the lack of muzzle flash and noise it produces at night.
I also have a Gemtech Tundra for my Glock 19 and though it's cool to shoot, I don't think it is a useful as my 5.56 suppressor.