Hi Werd
Since I fell out of the crib many years ago I started life with a compulsive disorder to disassemble things and then put them back together, until one day my dad gave me a thoughtful insight "son if it's not broken don't fix it".
Needless to say I ignored my dad's advice, as there's always room for improvement.
If Bryston changed things there is probably a good reason, and that reason is always to come out with a better solution to improving sonic accuracy.
So I do not doubt there is an improvement over the earlier SST's, but I thought that because the differences in the Squared units from the 4B and down were less extensive than the 7, 14 and 28B?s that Bryston might possible offer an upgrade to the lower line.
I'm sure I am not alone in bringing up ones SST to current specs without the need to investing in a whole new amp.
Robert