I am happy to hear you have the ...4446 - I find it remarcable.
In fact, I do not like anything else mentioned on this thread more except the nearly octagonal VS2, even so - this is just a matter of taste & love of included crystals, so I am not insisting that you call the thing in.
Slightly above 20K, I am finding a 2.11 E/VS1 that is a little larger & apparently nearly as nice as your find; perhaps worth taking this one in? WWW
I would certainly call this other joint & ask if they have a square step cut within your specifications - for perhaps the worth of both BN stones together, there is this WWW - a detail of the GIA report makes me assume it is not twice more again, but I do not really know. I must have been lucky to have a long conversation with the cutter in charge & I am not about to forget that one.
That big one from GC is pretty, but I'm fairly certain I've reached a soft cap for the amount I'll spend and still be able to sleep at night, lol.
I mentioned in another post that I'd like one more stone in-hand with which to compare ...4446. What do you think, AV (and anyone else reading)? If you could match ....4446 with one of these other three, which would you like to see?