Even tho I'm not now nor have I ever been a golden-eared audiofile, I believe that EVERY change to an audio system makes a difference in the sound. Whether it's one I or you and anyone else can HEAR is a separate question.
I agree that the aural differences among similar-priced capacitors is minor, but I
have heard the differences. I believe that it's well worth the money and effort to upgrade existing crossovers and PROBABLY worth the money to have them
built with higher-quality components. This, however, can be expensive, as one can easily spend $100 on ONE cap!
On quality by brands, I believe that Solen 'propylenes are enty-level high-end caps that definitely sound better than the typical inexpensive 'lytics. Beyond Solens, the sky's the limit. Some have mentioned V-Caps and other brands that I expect sound very good. I've used lots of NorthCreek Harmonys (1uf and 0.22uF) (here
http://www.northcreekmusic.com/Zen.html ) as coupling and bypass caps; I think they're good- to very-good sounding and are GREAT values. Maybe Solens bypassed with Harmonys would be my entry level. Depending on the values, probably I'd use (and I
have used) Rel-MultiCap 'styrenes and TRT DynamiCaps, but their prices add up very quickly. In a single-order, three-way crossover, there are only 2 caps, so maybe this quality level (that I call 5-star in the case of D-Caps) is affordable. I've used Mundorf M-Cap Supreme Silver/Oils as couplers in a SET amp and regular M-Cap Supremes as PS bypasses, adn the music thru these amps sound better.
Marbles, if you can find out what values and counts are used, helping you select caps would be easier. For instance, selecting a 2uf cap is easier than selecting a 20uF cap.
Read Mike Elliott's comments on caps here
http://www.altavistaaudio.com/caps.html.
