Hi:
I own a mint set of B's. I worked with Peter Snell's dad and his brother (Tom) for a while (long after Peter's death), so I have this deep mystique over Snell speakers.
The B's have shattered that blind faith in me.
I have had similar problems in "bringing them to life." For months they sounded more like instrument amplifiers hooked up to a turntable (ugh).
I own two sets of Snell A's (wonderful) and a set of C's (also great), but nothing came out of the B's that approximated that level of listening.
I switched out interconnects, speaker cables, amp/pre-amp. Added a sub woofer at one point, and then finally called Snell completely frustrated.
You can still reach them (use Google) and the company is still great. I spent an hour with an engineer and he basically said that these might be the worst Snell ever made from a user's perspective. All the right components in an odd shape that most people do not deal well with once they get it home.
Here is what I took from the conversation and it has helped me.
Use lots of power and listen moderately and these will begin to live for you. I use the upper Adcom amp and preamp with the gold fronts, I think it is 300 w/ch. I switched to Tara Labs thick cables and Tara interconnects (getting away from silver Kimbers and speaker wires) and the sound mellowed nicely.
Still, they sounded like Bose 901's turned the wrong way in a room.
The best information he gave was to use the Snell A speaker placement instructions and forget the speaker shape of the B's. Line them with the drivers facing front and start about 8' apart (nothing in between the two speakers) and 2 feet from the back wall. I find the closer these come to a room corner the more they lose fidelity.
Try the back tweeter switch on high.
What that gave me was a Snell speaker. Before it was a sense of idiocy for not being able to run the set since I trust the company name.
So I kept the B's. I like them more and more. They are not my best speakers, but they are nice speakers and the look of the case is attractive and the drivers are not going to wear out (from cone rot) ever.
I do bi-wire. I don't use my tube equipment on them. I do find that they are really sensitive to room acoustics and placement. More than anything I have ever known.
But... find the sweet spot and listen to a favorite tune and you will smile.
BTW, even the famous A's need time to find a spot in your room before they offer life-changing sound. The B's are like the A's finicky, spoiled siblings. Great DNA, but a nasty placement temperment.