What money are you looking to spend OP? That would help point you in the right direction. If you want quality and don't mind spending up to $250 then get a Centurion Arms C4 rail. Scalloped rails for comfort and mounts using standard barrel nut. If $250 is too much then look at the Fortis Rev 12, lightweight and also mounts using the standard barrel nut
I had a Midwest Industries drop in quad rail on the other AR I had, was super easy to put in and seemed nice. I liked that it had built in QD points as well, and not super expensive.
If you are in the area come by the shop and we can show you a bunch of different options. We stock many different styles and brands of rail systems.