That depends on how the balanced B22 was configured for gain. If it were mine, for example, you're probably right since I'm only using a gain of 2 per board (effective 4 per channel). However the B22 can be configured with more gain (2x, 5x, 8x, and 11x). If it were configured for 8x or 11x, it should be more than enough. I would even think 5x would be enough. It just depends how loud you really want to listen to them. I use dynamics and not orthos. With the HD800 and a gain of 2x, the loudest I ever use it would be the 12:30 o'clock position on my attenuator. The HD650s seem to require a little more power so I can go up to maybe 1:30 - 2:00 on the attenuator. But I never max it out which would be the 5:30 position. Obviously the orthos require more power but I'd be the B22 you listened to wasn't configured for a higher gain.
It wasnt that it didnt get loud enough, it ran out of steam when you tried to listen too loud. The soundstage started getting pretty constricted. at lower volumes it sounded pretty stellar, it just didnt hold its composure into volumes that i would more regularly listen to. Anywhere below like 12 oclock on this particular B22 sounded amazing, but when you went above that is when it started running out of steam. I believe they had each board configured to 8x gain? Im pretty sure it was the power supplies. I surmise that maybe have 4 power supply boards, one for each amp board might mitigate the issue.
So i guess in leu of this that maybe a Master 8 would work, since it probably has a beefy enough power supply...its just i really liked that i could use the Master 3 in the future when i do have room for speakers...alas, i have some months still to decide