Stripped Stag lower, DPMS lower parts kit, CAA 6 position stock, YHM 2 piece 4 rail hand gaurd, and a complete upper with 14.5'' M-4 barrel with the A2 flash hider blind pinned to the barrel from M&A Parts.
BCM or Spikes. A few bucks more can get you a Daniel Defense. You'll get individual HPT & MPI parts, 4150 chromoloy vanadium steel barrels, M4 feed ramps and the closest to mil-spec your gonna get. (since tru mil-spec rifles are select fire.)
If you dont need a hard core capable rifle then an M&P or Stag or RRA is GTG for about $800 in my opinion. Stag is the only mid tier AR maker I know of that clearly states it has a lifetime warranty so thats a nice selling point there.
There are a LOT of barely used AR's on the various classified boards right now. Search the boards, buy a lower and whatever upper you want. I put together an LMT lower with Sopmod stock and LMT upper last week for $700 + $25 transfer fee. $725 ready to shoot.
With all the AR's on the forums right now, buying new would be my option of last resort. So many people bought AR's during the last presidential election and now need the cash - they're dumping them for cheap.