Despite the naysayers and even Bryston's recommendations, an aftermarket power cord can make a big diffeence in what you hear. I've tried several - Harmonic Tech, DiMarzio, Silver Audio - but have found the best for my 4BST to be the Analysis Plus Power Oval which gives the 4BST greater dynamics. It is an audible and positive difference.
It's worth a try to see if you hear a difference that you like.
It's worth a try to see if you hear a difference that you like.