I will be buying a Rock River Arms lower at my local gun shop for either $250 or $350 depending on whether on which trigger I want. And I will be buying a complete upper online. I'm looking at either a Rock River Arms or Stag Arms uppers. I can get the RRA for $430 and the Stag for $375.00. Both are flat tops and I'll have to add a rear BUIS. Which do you recommend? Is the quality of the Stag and less. It will be mostly used for plinking and under 100 yds.