I got a RRA 18incher, love it! It is really heavy though! I would recommend getting the normal flattop, not the EOP, and no carry handle. These things are meant to have a scope on it, so no carry handle is needed and the EOP will place the scope to high for a comfortable check weld IMHO.
Now since the barrel is so large no muzzle break / flash hider comes on it, and i think it would look really goofy putting one on it since they would be smaller than the barrel.
I got mine from steve at ADCO, check out his page, he might have some in stock, he seems to have ones in stock when nobody else has em!
www.adcofirearms.comanother good place to check is Pete at legal transfers, he also has RRA stuff when no one else seems to.
www.ar15sales.com/I have order from both, both are top notch!