Of all the lights I have, my personal favorite is the Elzetta Bravo (I have the 235 lumen model). I like my surefires, but the Elzetta just feels more robust and like it would take much more of a beating, which I found to perfectly complement my AK, which is set up as my primary SHTF rifle. Light is plenty bright as is in drop in config., I'd get a different lens though if you want more flood. Plenty of reviews and information out there. It is a bit more expensive than the budget lights, I got mine from maxprotactical for $151 shipped, worth it imho.
From RSR, are you getting an accessory mount or optics rail? I have an RSR 301 side mount mated to an AKR upper half running a Lucid M7, the quality of the rail is unmatched in any other rail I have had hands on experience with, very good products.