One of the reasons I am enjoying my first SET 300B amp so much (besides the excellent EML 300B XLS tubes), is the caps were upgraded with the new Jupiters. There is no doubt they are a major contributor in making an otherwise inexpensive amplifier sound so much better than any other amp I've owned.
Curiosity, though, keeps dragging me towards Dueland caps, most likely to replace/compare against the Mundorf silver-in-oil caps currently in the Tannoy outboard crossovers.
In that, Charles, you are a bad influence on me, as is all this talk of better performance with the uber-expensive Duelands. Always a better widget out there.
Regards,
Dan