If you were going to go 6mmARC and use on your 223... then I say Wolf Hunter from Diligent Defense, or the new 6mm that Otter Creek is coming out with.... otherwise, I'd say, go with the Enticer S from Diligent Defense or the Otter Creek Labs Polonium 30. With 30 cal cans, they will generally lose some suppression of sound with anything lesser than the 30 caliber it's intended for, however, the 6.5 Grendel and the 6.8SPC are intermediate in velocity and suppress quite well with both of these cans. I do not have an explanation, but Jay with Pew Science has discussed their signatures on the 308 to give a baseline of what to expect from them.
Both of those cans mentioned come with HUB compatibility and allow use of many different style of muzzle devices. I personally own the OCL P30 and shoot 6.8SPC and several grendel shooting friends have the Enticer S (along with several other cans), and choose the Enticer over their other 30 cal cans because of how well that the Grendel suppresses using the DD.