Build it out, burn it in, listen for awhile. It is much easier to troubleshoot a stock build and you then have a sonic signature basis with which to compare mods. Boutique caps are, in fact, expensive, but not necessarily better. It really depends on how you want the unit to sound and other components in the audio chain. Some of the best sounding caps, with top notch construction are old American and Soviet paper-in-oil caps. When you compare them to the cost of Jensens, AudioNote, Dueland and other newly manufactured PIO caps, don't let the cost differential make you think the more $$$$ the better cap. Russian Teflons, especially the FT series are also well regarded in the DIY community. Most of us could never afford the cost of the Russian caps if they were being manufactured today in an open market. Think of it as the Cold War military budget subsidizing your audio habit!!
Search and read through forum posts on what others have used and why. I would put fellow forum members opinions and experience well above any online cap survey, especially one that compares the caps in speaker crossovers, not amplifiers. (Although cap construction materials all have a sound signature, plastic caps, plastic caps in oil, PIO's have family similarities) Make sure that the caps, are for you, "ear candy" not "eye candy"!
Have fun building, then enjoy customizing to your taste!!
Cheers,
Geary