My current solid state DAC utilizes a toroidal transformer (And it sounds wonderful). I’m currently having a new tube DAC built for me that will have 3 separate toroidal transformers (Also 2 chokes) so a fair amount of iron. Both my tube preamplifier and tube mono blocks utilize “double C-core” transformers and they sound wonderful.
I suspect that like virtually all things concerning audio the major influencing factors are quality of construction and execution. I believe that in the right hands, all of the various types of transformers can contribute to excellent sound quality performance. It is however interesting to explore why different builders chose to use a particular type of transformer.
Charles