Colt 6920 is more or less the standard on a M4 pattern rifle.
Olympic, DPMS and the "Off brands" are generally the "lower teir"
Noveske,Rainier, Daniel Defence, POF are generally the "upper teir" rifles.
So now you need to find something in the middle. LMT is worthy of consideration as is an older Bushy. I would take a Smith and Wesson over a Stag. Colts are damn good rifles so don't discount them.
Bravo Company are great for the money as is CMMG. Rock River is not too bad.