I just tried the 4 ohm on my bryston, and with that amp(3b), the B+Ws sounded much, much better(than the 8ohm where I normally have it hooked up with that particular amp--the bryston and b+Ws are always paired). The VSAs still sounded Anemic and source localization was still lacking with the 4ohm on the bryston.
so it truly is dependent on the speaker, an maybe speaker + amp combo..?
something to try though, 'cos otherwise you will never know...