I tend to like the polypropylene over the polyester but Joe may chime in..... Will it make a diff??? Maybe, maybe not, but that is the fun of it if you like to experiment. Most of all? Have fun listening....
There are 8 polyester caps which you COULD change out (for polypropylene), but you may not notice the diff.... Shit, some caps change values during operation from heat/freq/drinking, and if you want to experiment to make your amp/Pre fit you system/ears... I say GO FOR IT or.... Maybe not... I experiment a lot.... Some things work, some don't. but, how ya gonna know... Sometimes, you can't find caps in the form/material/function so you get what you get.. Sometimes, the designer saved a few bucks.....
P