Tubes can make a difference, to be sure. So do caps. However, the losses in a capacitor are well understood and documented. I get suspicious on capacitors that state they are '... so much better ...' but give no specs other than some mechanical dimensions. Sure they might be good but how would we know? Buy them, find out, and then discover they are not returnable? Hardly.
Don't get me wrong, they might be great but without a datasheet and some loss specs, I am not forking out any of my money. Without that, we are only guessing they are better than WIMA, who does publish the loss specs.