I have the Magpul hunter on a RAP. Works well. Its a good blend between options and price. Some things I really like about it (weight, AICS mags, LOP), some things I do not (cheek riser system). At the time the only choices were a Boyds, Stockys, Magpul, and MDT LSS system. I went with the Magpul. You should definitely look into the new MDT Oryx chassis. It is available for the Ruger American series. It wasn't available when I was making my decision and I sure wish it was. It checks all the bells and whistles I wanted at a reasonable price. After adding bipod mount, QD sling mounts, and a different height cheek riser I am into that Magpul Hunter system for what I could buy the Orxy for.
*edit. Looks like I still would have had to purchase M-lok accessories for sling and bipod mounts with the Oryx also, but I still would have gone that route. For a little bit more it seems like a much better system than the Hunter.