I'd stay away from the stag, some shoot, some don't.
The kac's are beautiful rifles, but a bit overpriced, and the accuracy isn't proportional to the price.
The lmt's are accurate with the rock barrels, but it's kind of a limiting platform should you want to change anything in the future.
Atrs is an option, but I had a friend that had qc issues with his upper to lower fitment...
I'd go with a build from armtac, as he can get the good stuff when it comes to parts.
Do a vltor upper/lower with a noveske ss barrel.
He uses vltor/bcm/noveske components, so you end up with a top grade ar, and the noveske ss barrels are universally sub moa with 75 grain hand loads. Consistently sub moa. Not "shot a sub moa group a couple times" sub moa.
Here's one he built for me last year with a 16" noveske lightweight barrel.

Very high quality barrels, even with the lightweight profile, there is no shift in poi with long strings of fire. Sub moa, and light enough to be used as a carbine. One of my favourite rifles.