Avatar is at the opposite end of the market from fEARfuls and the like, and don't claim to be otherwise. They could take the alphalite from the TB153, or us an la6cbmr, with the same HPF (and likely LPF for the 4ohm 212), modify the LPF for the 8ohm version and have a winner IMO. It doesn't need to be "perfect", just sound good, which it will. The closedbacks in my Pa cabs would distort with appreciable power put to them, but that's with a typical 500hz off-the-shelf crossover job. I put the same closedbacks in my bass rig, pass them up around 800-1khz and the distortion isn't a problem anymore. They are a little rough around the edges compared to premium stuff, but Avatar isn't competing with premium stuff. They'll still sound way mo' betta/more "professional" than your typical 410's, etc.
The box is already there, the filters are already there, all they'd need is a different LPF for the 8ohm woofer compliment version, that's it. It's just more switching around/using different combinations of what you already have for the most part. 1 of those mids runs hot enough to sound good with 2 woofers. I run that way all the time, and frankly, wouldn't want some 100db 6, I'd just be turning knobs trying to tame it down anyway.
Now........about that JTM45 clone.....hmm....