Although I have the MOE on my Carbine, I have also considered going for a quad rail on my 15OR.
My research leads me to believe that the Daniels Defense Omega, free float system makes the most sense for a simple instatllation of a high quality rail system. The surgery necessary to add anything but a simple drop in rail to the OR model with the same height gas block makes that the choice worth spending the bucks on for me. I see too many problems reported with the fit and solidity of the dropins in the lower price ranges.
Honestly, without intention of adding lots of "tacticool" **** to the forend, I may just stick with the Magpul which fits pretty well on my rifle. Just have to fight the "fever".