I've got a HVT-QD for my M1A, so I needed to get a new muzzle device. Got Gemtech's Quickmount; looks like the old Phantom flash hider.
Then, seeing as how the mount requires you to remove the front sight, got a Smith gaslock front sight.
Then, seeing as how the M1A will send volume of gas to your face, picked up a few USGI breech shields (part of the blank firing toolkit).
The design of the rifle doesn't lend itself particularly well to supression; the open action adds some noise.
ETA, still using standard gas plug and it works fine.