The first build, we spec’d great transformers and Mundorf caps. I had the chance to compare 5 builds including some that were closer to the original Western Electric design, and a few with larger transformers that weren’t as boutique, but where the 300b was putting out over 10w. The Western Electric amp design was awesome but lacked low end, so we used the nickel transformers.
I think the transformers made a big difference for the bass but initially the bass felt like it was soft. We swapped in larger Mundorf caps and wham! It was like adding half an octave of bass, and brought the performance within spitting distance of the EL34 amp. The caps added $600 to the build, but well worth it. Total cost was about $4k including the Gold Lion tubes.
I will say the O/96 reveals every change, especially cables. It gets better the more you feed it high quality stuff.