I just put two new .1uF Jupiter Coppers as bypasses in my Duetta Sig crossover, one bypassing a 15uF section and one bypassing a 10uF section, each containing Sonicaps. They replaced some Russian teflons that just sounded a bit too forward and hard when things got loud.
Well, that hardness is gone. The extension is there. I don't hear any of that discontinuity that sometimes accompanies the use of a bypass cap. Very natural and balanced with no over-emphasis at any frequency. Space and air as good as the teflons without any drawback that I can hear. Took about 100 hours or so to get there though.
I also used the new Jupiters (1.0uF) as the coupling cap in my phono stage. Just awesome. Read the few reviews that are out there already. I hear all the same things they said, so I won't repeat it here. I don;t have Duelands to compare them to but I am a happy purchaser.