The TBAAM is USB powered, so in some ways I'm impressed that it gets this far. It plays loud, and I've got both Speaker and Wav volume sliders at about 15%, but that may not provide the right load to take bass as far as it can go.
The 900 might perform better through better hardware, then. Or maybe the only difference is a few microns of paint, and the gullibility of folk like me. We'll find out pretty soon -- thanks for sating our collective curiosity, spliff.
Moving on: A few hours of listening time on mine so far. Going through the process of rediscovery that comes with all drastically different headphones than those you're used to, as some songs now sound awesome and some sound like crap. They're more detailed than I'm used to; I imagine that one would be hard pressed to get this detail out of a new off-the-shelf can for the price. Lots of new information coming at me from frets rattling and strings squeeking. Drums have more snap, despite not having the same meat as the RP-21.
I want 'em to feel like they've opened up. Maybe tens of hours of burn-in will do that, or an amp that properly loads rather than just playing loud. If I crank the volume a couple notches higher than I'm comfortable with, it starts coming through more clearly. Hm.