Bill,
I've heard a lot of good, and bad, about the Mundorfs. I can't say that I've tried them myself. Basically, people seem to like them initially, and then don't after a while once they are fully broken in. They seem to have a bi-polar reputation.
The Apogees are still very smooth and not aggressive in the least. I'm trying to improve the openness and bloom while still retaining their overall tonally even character. I think I might have gone a bit far one way and want to see if I can bring it back a notch with the PIO's as I move into the "second half" of the crossover.
The Auricaps were recommended to me by several Apogee owners who have upgraded their crossovers, so I used them in my original mod of the Calipers. They are clean and open and transparent and fast, but I also tend to find them a bit dry with maybe a bit of a loss of harmonic richness and a bit of plastic sheen. Anyway, I've got them and I used them. They may be the real culprit in what I am hearing now.
I've found Sonicaps to be one of the most balanced caps around for a crossover, with a very even character - not overly warm and not shrill in any way. Yes, they are open and fast too, but they retain that harmonic stuff that makes the magic. They work very well on the bass too, being extended and tight. They are my "go-to" cap when I want to keep things on an even keel, and allow me to tune things with the other outlying caps.
I know I will get where I want eventually, but it is fun to learn new things as I play a bit.
After all, I'm not in any rush and have all winter to experiment (that's typically my audio play time).