I currently use the M50, AKG Q701, Philips L1 and Shure SE215. I keep the bass boost on because, you know, the bass lol. I'll use the Q701 with the high gain. I might not need a better amp now, but later on I plan to buy other headphones that may utilize the amp to its potential. Plus, I've read about how much people like using this amp. At the price I see it on Massdrop, I wouldn't mind having a taste of it myself.
This brings up another question, would I still be able to use the bass boost on the e10k if I combine it with the O2 amp?