If you want a truly quiet gun pick up a TM AEP and throw a silencer on the end. Obviously the silencer does not have the effect of a real can but it does mute the sound somewhat. I have an AEP with a handful of different silencers and it is by far the quietest gun I own. The range is not quite as good as an AEG but its compact, can hold plenty of rounds and is quite dependable. You can then use your AEG for the majority of your firefights as the need for a “quiet†gun is limited.
Warlock out of curiosity what type of Dynamat are you going to use? I wouldn’t recommend using it unless you modify it somewhat.