I have inexpensive Jantzen (2.2) red colored caps in my Bottlehead Paramours that sound excellent.
Been thinking about going SS, but if I don't I may try the Jantzen silver colored caps which are said to have a bit more detail.
I don't recall what was in their originally (been using them for 20 years now).
I looked @ Audyn copper when they first came out, but 2 of them cost twice as much as I paid for the amps/mono-blocks.
However, if you go with Zipost's advice don't stop there as you can also downgrade your speakers, cables, source gear and maybe even the tubes if you are lucky.
DeKay