The house sound from BAT tends to be a bit darker than ARC. The criticism of BAT is that it's a bit on the dark side. Criticism of ARC is it's not "tubey" enough. I happen to disagree with both criticisms. I'm a big ARC amp fan, especially over the last 5 years or so starting with the Ref 150 amp. On the other hand, I have not not heard a BAT product that I did find alluring with a dash of that darkness that can sound seductive. Both companies stand behind their product. You can't go wrong.
But as for the Ref 150se or GS 150, these are the 2 best amps in that power range that I have ever heard. These are very special amps.
But as for the Ref 150se or GS 150, these are the 2 best amps in that power range that I have ever heard. These are very special amps.