Call the guys from Griffin Armament and ask about their M4SD II. It fits over normal flash hiders. I think they usually have a spacer that goes behind the flash hider but I have seen one used with no spacer. I've got one in ATF Hades but have had a chance to shoot it. The sound quality is good - and I've got Surefire, AAC, TBAC, Silencerco, KAC , AWC & SAS suppressors.
http://griffinarmament.com/silencers...lencer/m4sdii/
Yes you can remove a pinned and welded flash hider and have a brake put back on (I've done it). Both Surefire and ACC have Brakes/Hiders that have predrilled holes to pin the muzzle device.
Another thought, get the SF 762SOCOM Mini. It's a .30 cal but it allows you to use 5.56, 300BLK, 308, 260, etc… The full-size 30 cal cans suppress better but the Mini is the same size as the 556 can.
A cheaper option is the SAS Reaper - A small company that does their sales thru Mile High Shooting Accessories.