I just got my B60 back from Bryston Canada. It was an original B60, now upgraded to SST status. The mids and highs are what improved the most - more clarity, resolution, and better cohesiveness (if that's a word). Basically more insight into the music.
It had to go to Canada (I'm in the US) for it. Easily the best $115 I've spent on it. Far better than any cable change or tweak I could have thrown at it.
Not sure if yours can be upgraded. Mine is a 1999 model. Call Bryston Canada and talk to Mike Pickett. If it can't be upgraded, maybe look into buying something like a 2B SST? I'd imagine that would be better than what you or I have. You could use the B60 as a preamp.
Great combo BTW. I really like the Arros. One of my favorite speakers regardless of price.