One thing to note is that if you purchased a latter model SST (late 2008 or old stock in early 2009) you would have the SST2 internals with the SST badging. SO in such cases an SST will sound exactly like an SST/2.
GaryArthur - could this be your situation?
You bring up an interesting point regarding Bryston and model changes. For example, the earliest models of the 28B-SST did not have the toroidal transformer made by Plitron whereas the later 28B-SST's had the improved transformer, improved power switch, caps etc... I'm not sure if there was any difference between a late model 28B-SST and a 28B-SST^2. The early models of the 7B-SST^2, I believe did not have the new Plitron transformer and the later models of the 7B-SST^2 do.
However, my 4B-SST^2 has a Dec 2009 manufacture date and I believe my 4B-SST was made sometime in 2005. I'll check on the exact date when I get back to Vegas. Still my solo observation was that there was little if any sonic difference between the two. I'll do some more comparing soon. Maybe even bring some friends over for a double blind test.
By the way is Bryson ever going to put the Plitron transformer in the 4B-SST^2?
Regards,
Gary