Hi PMCIB2fan,
According to "Pro Audio Review" the first 25 watts put out by the 7B are class a (hopefully James can confirm or deny this). Go to the 14B SST page on the Bryston site, click on the reviews tab and the review is at the top of the list. The 7 is the same amp as the 14 broken out into two chassis. It would be difficult for anybody to comment on the degree of upgrade the 7B would make without having heard both in a variable controlled audition. However, it seems logical to me that since the SST came out in 2002 and the SST2 in 2009 that either might be a technological advance over the circa 1994 Aragon. When you consider the class a operation and the list of performance based enhancements in the SST2 taken from the 28B it should be a safe bet on a significant enhancement.
Curiously, you and I may end up with the same system. I'm planning on upgrading my electronics to 7B, BP26 and BCD-1 to drive my 18 year old Infinity 9 Kappas. I have to do so without the opportunity to audition so if it doesn't work out I may sell the Kappas and take a strong look at the IB2's as I know they have great synergy with the Bryston line. I'll hope to see a review from you if you go for the 7's.
Thanks,
Bill