Krell KSA-250 Rev. B?

I came across a wanted ad looking for a Krell KSA-250 Rev. B. I did not realize there is a B version of KSA-250; anyone cares to shed some light on this mystery?
I could be wrong but I think the ksa was changed to stay in class A mode to a higher output. I think the rear of it is layed out like the ksa-300 also.
Never heard of it. The prior marks of Krells
(KSA 80 and 200) initially were only single-ended, and there's a -B version of them to indicate a balanced input on the later versions, but I thought all the KSA-250s had both balanced and single-ended inputs. You might call Krell, they're good about this--maybe it relates to a factory upgrade?