Caps I have tried?
Here we go...for a start.
Mundorf S/O: very nice, good staging ect' but a little lightweight down bottom.
Obbligato Premium Gold: have them in my crossovers on the tweeter side, I like them...seem to add weight/warmth.
Obbligato Coppers: in my crossovers in the remaining positions 'as above' but a little less smooth maybe? but that's splitting hairs.
Obbligato MPK's (the black ones): used them in a Sansui AU-555 instead of small value electro's, seemed to be fast & dynamic.
Auricaps: had them in a pair of Richter Harlequin Mkll speakers, nice enough.
Russian PIO's: warm and smooth but wooly bottom and rolled off top, a bit smeared over all, I think.
Russian Teflon FT3's: smooth and transparent but too polite for my liking, a touch synthetic sounding.
Aerovox 470uf/500vdc screw terminals: these were used and in my amp till today.
Mundorf M-litc HV 200uf+200uf/500vdc: these replaced the Aerovox caps above and sound wise blow them out of the water, even without much time on them.
Meh..can't think of others off hand, and as you can see my experience is limited.
My opinions on sound could well be a result of the application, mainly to do with components working with them/along side them, hard to isolate the sound of a single component completely IMO. That synergy thing, system dependent...
Edit:Trying some Chinese Mil' surplus film & oil caps instead of the Mundorf S/O caps in coupling duties now, will wait a little before commenting on sound