the remington r-25 (ar-10) comes w/ a 2-stage trigger, and a medium weight barrel. it is a fairly heavy rifle once you get optics on it. very accurate, and p-mags available. the mag that comes w/ the rifle is a 10-round mag. mine came w/ blocks so i could block it to 3+1 to make it legal for big game hunting. since 5+1 is legal in my state i trimmed the blocks to accept 5, and then ordered p-mag 20-rounders. so i have one legal-to-hunt magazine, and the rest are for whatever.
the trigger is decent - not as good as expensive triggers, has a little bit of drag, but good enough that replacing it isn't worth the expense to me. i haven't weighed it, but i would guess the second stage breaks at 3.5-4.0 pounds. it is predictable and consistent.
traditional detacheable carry handle mounts would work fine on the r-25. you'd have to come up w/ a solution for the front sight, but a carry handle would work fine for the rear.
as far as stag... my ar's are built from stag lowers. they have been very good, but i do not have experience w/ stag uppers. given my experience w/ stag lowers i wouldn't be opposed to using a stag upper, but currently have no need.