stag arms makes some nice out of box guns for a fair price
BUT as others have stated
WHY do you want one, and want it FOR< can make a difference on suggestions here
plain jane NO names can be had CHEAP< sub 500 at times, and HIGH end over the top can be a few grand
Basic bushmaster's are always on sale here for about 550-650 in a m4 like set up
things to look for on some models is, barrel type, rifling, if it has Forward assist or not, a threaded barrel or NOT
as these things can matter as to WHY and what you plan the rifle for!
I sold a few thousand of AR's when I had my shop, so??