You don;t want the old AAC SCAR suppressors... they use the crappy old 18T mounts. If you have to have an AAC suppressor, get one with the new 51T mounts.
I use a Gemtech G5 on mine and am vary happy. It's about as quiet as a 5.56 can gets, it's got a good compromise in size and weight, and the I like the QD system. It has a consistent (and small) POI shift.
But any of the top can makers will satisfy... AAC, YHM, Gemtech, Surefire.... just pick the one with the features you like best. Don't get wrapped up around metering numbers. Your ear will not detect small differences. The top cans all suppress well, and are quiet (for a 5.56 can).