Okay, I know this is an old thread, so no need to bother unduely, but: I've now tried a B7, and it's an solid piece, though not as convincing as the M7 (if you ever get to try one, hgiles, do so - it's worth it!). What I found really interesting was to compare it to a Selmer S90 and S80 - the B7 did hold its own in that comparison, which could count for a lot! I think that at leats on the B-6, I could easily replace the S80 by the B7 (the S90 annoys the hell out of me anyway, so it's no contender). And what's more, the B7 also works reasonably well with the New King bari - that's something to write home about, the Keilwerth is a very fickle horn indeed. The Ricos provide the best way to control the intonation on this horn, by the way. For the price, the B7 is a very, very good mouthpiece. The Metalite M7 (especially my older one) still comes out on top, though.
M.