Dear Volleyguy: Nice thread and a lot of fun you are having.
Speak about caps and caps's quality performance is almost always a relative subject opinion not an absolute one because any one of us have different music sound quality reproduction priorities and likes different kind of " colorations " due to audio system own limitations.
You are looking not for a " neutral " cap but for a " colored /distorted " one: +++++ " I want a warm not overly detailed sound .......they need lush smooth sounding caps " +++++
Nothing wrong with that it is your choice.
Of the passive electronic parts de caps IMHO are the ones that show more colorations/distortion and that you can hear it. Over the time I try several caps looking for the less " colored " one, looking for neutrality and one of the reasons that I was looking for neutrality was that a neutral cap ( in the speaker croosover ) is a way to know if the whole audio system is really right on target, a neutral cap can/could tell me if I have " problems " somewhere in the audio chain.
What happen if I choose a " colored " cap that with is own colorations hide those system quality performance in the audio chain?, well maybe I like it ( like in your case ) but what we are adding is more distortions to the final signal reproduction and ( at least ) for me this is not what I like to have and hear, my quest is to be nearer to the recording and this means: no distortions/colorations/noises/degradation on the signal trying to mantain its original integrity and this means too: accuracy and neutrality ( not analytical, lean or cold performance. ), looking for the less signal degradation in each link in the audio system chain.
Why I give you all this explanation?, well things happen ( and I'm not saying I'm right, it is only my opinion. ) that I already try/test ( over the time ) the Mundorf, Sonicap, V-caps, Duelund and many many other to name it here.
Till today I don't find any less colored/distorted cap that the Sonicaps. The Mundorf, Duelund and the like are not a neutal one items: far from there ( IMHO ).
I know that you don't like the Sonicaps and you know why you don't like it?, because it is telling you that your audio system has several quality performance " problems " in different audio links ( your vintage ones caps are too colored and yes I know the Scala: I owned it. ).
Do you know which is the signature quality difference performance between a distortion audio device ( cable, caps, resistors, inductors, tubes, etc, etc ) and other with less distortion?
well it is exactly what you report from the Sonicaps: " I hear less volume ", NO what you heard was not less SPL what you really heard was less DISTORTION that you " feel " like less SPL, believe me no doubt about.
Merganser already posted that you are not given the time to the different caps to settle down and I agree totally with him and I think that like me he is trying to help you.
In good shape let me to tell you how I'm looking you about this new " toy/game " to you: like a child with new toys that take it one and then other and the other and other: a lot of fun but almost nothing ( IMHO ) that really could help you in the long run, of course that it is your time and money.
Other thing that I'm worried about is that you are taking the opinion of those guys that made several test on 30+ caps ( the link that you posted ) where you don't know its real music/sound priorities and worse than that where you don't know how high or low are the distotions/colorations of their audio systems.
Along that the opinion of them about to " tame " the caps performance mixing different caps tell me that those people are not the best experts to take in count and let me explain about:
what they state and you follow is that you can compensate the distotions/colorations of one cap with the different distortions/colorations of other cap.
So what you have here is an absurd by any standard: that from two different colored/distorted different caps you achieve the right one!!!!!!
I'm sorry not agree with you about: from two distorted/colored caps ( adding its distortions ) you achieve a heavy distorted/colored performance not the inverse. That what you hear like it or not it is other subject but the reality is that you have more distortions. I don't like it but the important subject here is that like to you.
Regards and enjoy the music.