Out of curiosity why do you like diaphragms over pistons?I like diaphragms, I've owned the G260 and MK17 numerous times. Based on my experience the G260, in my humble opinion, is one of the best second stages by SP, maybe the best ? Still evaluating the D420. Despite its sometimes large ip swing the MK17 is solid. I've zero experience with the C series. Shopping is fun, owning your own gear is more fun. Good luck.