I'll chime on here with my experiences and mind you this was in a coupling position on my amp.
I have had Auricap, Mundorf supreme, Mundorf Silver/oil, and Vcap. I have had hovlands and Cardas in other amps too but can't compare in this case.
I hate to use the usual audiophile jargon so I will just convey which were the best and most natural sounding. To me, I tend to prefer what sounds natural and real, you know, what real live unamplified music sounds like.
In my amp the auricaps although better than the stock solens were the poorest of the lot. While the Mundorf S/O's sounded nice, for some reason, I can detect silver in the signal path in my system and don't like it. It sounds un natural. I feel that for silver to work, the circuit has to be designed for silver.
The Mundorf supremes are quite good and excellent for the money. I loved the Audio note Coppers but they are massive (1uf) and would have to modify my amp to make them fit. And that is what I would have done if not for the Vcaps. The Audio notes are great but the Vcaps are amazing. How? it has already been said above.
So my advice is to splurge on the Vcaps. If they cost too much, try the oimps or the sonicaps as suggested above. Or if on a budget, the Cardas or Mundorf. There is a cap shootout on the Vcap website. Keep in mind that your preferences may not be the same of that author's. He rates the mundorf silvers above the silver/golds (which I have not heard) and the supremes. I did not care that much for the silvers. As they say YYMV