Well, I do have the CBM 170's and HTM's in an 5.1 set-up. I really haven't heard anything that will "out do" them. Just remember though, sound is so subjective. The 340's are quite impressive . . . from what I hear.
I don't think you can go wrong with your decision. Order, try 'em, send 'em back if you don't like 'em. You could order a single pair first to demo. Then add the rest later. Ascend offers a package deal; even if you only purchase a pair to start. You just have to finish the system within 45 days. Also, Ascend does not inflate S/H charges. My CBMs cost $8 to ship!
Yes they use Audax drivers; but they are proprietary . . . at least the mid-woof is. Looks like the frame from the mid-line aerogels, with the cone of the high-end drivers. Go figure, hey they sound very nice.
For the sake of not sounding like a shill for Ascend, there is some competition from Onix, Axiom, Aperion . . . all internet companies. I haven't heard anything in store (Polk, JBL, Klipsch, Athena, etc.) that will best my CBM's.
As always . . . YMMV.