The difference between an A-Tec and the old T8 is like night and day. I had a T8 on my Win Mod 70, and although the mod performed very well it did turn the rifle into an unbalanced plank, constantly slipping off the shoulder when slung and cumbersome to move from shoulder to sticks. That said, supression wise it couldn't be faulted.
The A-Tec CMM4 I've now got is almost un-noticable. The rifle handles much better and is a pleasure to stalk with. Supression wise it's not quite as good as the T8. The muzzle report with the A-Tec is a very flat "bang" with no resonance to it at all which causes no discomfort to the ears. On the down side I've found that this muzzle report is loud enough to mask the impact sound of the bullet. Being able to discern that was just about the only plus point of the T8 over the CMM4.