Many many many many many moons ago, when toroidal transformers first came on the market, a few intrepid builders tried making toroidal output transformers... and although they are better at efficiency and they cost about the same to wind, the whole idea never really took off as the 'puritans' amongst us complained that they "don't sound right"...

Technically it makes sense... at 50Hz or 60Hz the current make up of the ferric former of the toroid is ideal, but the same former for wideband audio use is not as it has different responses at different frequencies... find the right former with a ferric (or some other) make up that gives an acoustically appealing response and you'll be on a winner.... There are dozens of former types to choose from... Good Luck !!