I can’t answer the stocking dealers question, however from my research the AAC M4-2000 is superior, especially the 2007 model, for the same or lower price.
The NT4 QD attachment it about the same cost (~$100) as the AAC Blackout QD, however the Blackout is vastly superior flash hider.
I have first hand experience with the NT4 (I was issued one in Iraq) and it is a very solid unit. However they are very expensive and the suppressor design is outdated compared to other units.
I think Grant (GR Tactical) carries AAC, but I know Polite Society, Inc. carries both KAC and AAC, and is one of AAC’s primary dealers. I think you’ll be very happy with either silencer, but if I were to put a can on a barrel at least 12.5" in length, it would be the AAC SPR/M4.
I had an M42000 and it was a good can but if you can afford the KAC one Id get that one.Suppression is just about the same.Or you could get the M42000 and have a couple 100 left over.I know AAC’s CS is good and getting better and if you deal directly with Trey from KAC his CS will be excellent.
I love my AAC M42K. I further got an AAC 762 SD - this is a 308 can(a little longer than the M42k) with the same QD type mount for an AR10 and AR 7.62x39 barrel.
If I had to do it over and with only one can, it would have been the AAC 762 SD, since it works on everything 308 and below. That said you can never get enough of this stuff, can ya.