Having had two different 3 B ST's and now a 3B SST, I agree with your evaluation of the ST series-it bothered me enough that, although I liked what they did elsewhere, that slight brightness made the sound appear slight lean.
My 3B SST solved the problem . It is a very natural, smooth, neutral sound. Those looking for tonal warmth won't find it but,IMO, it is a significant improvement on the ST series. I'm assuming the same is true for the 2B SST but the the 2B LP ( which I also had) was quite different from the ST series.