I have a B210/B212 stack (both 8ohm neo in blonde) that I power with a Genz Benz Shuttle 6.0 and I absolutely LOVE it. The 2x10 is great for punch (and is surprisingly loud even on it's own) and the 2x12 adds some pretty thunderous lows (particularly with my P-Bass V with flats). Both sound great on their own, but man... the combination of the two is awesome! Before I got the 2x12, I was using the 2x10 at practices and it kept up with two electric guitars, acoustic guitar, keys and drums. The 2x10 alone is too much for my church choir (guitar, bass, drums, piano, sometimes trumpets/flutes/etc and 8-10 voices), and we play in a room that seats about 300.
I play a variety of basses, both active and passive, and they all sound great through my the Avatars and have their own personality, including my Peavey Cirrus 6 strung with piccolo strings. Even the 2x10 does a great job with my 5-string basses, both cabs have good mids and the highs are nice and present but not harsh.
I've also had the chance to hear my rig from an audience perspective with another band that "borrowed" my rig.

lol I was pretty impressed, and even the sound guys were commenting on how much they liked the sound.
It’s a
really flexible rig, too. Depending on what/where I'm playing, I can use either cab or both. Another great thing is that I always try to set up next to the drummer and with the two cabs, I can either set up the full stack or face the 2x12 to the room and the 2x10 directly at the drummer. Makes it quite a bit easier to really lock in the time!
As with any brand spankin’ new cabs, they take some playing time to break in, but both cabs got louder and deeper as I played them. I'm REALLY happy with my Avatars! So much so that I’ve been kicking around the idea of getting another 2x10 to try the vertical stacking idea.
5sg.