My experience with the same upgrade is almost the same, except I started with a Solen cap....mushy bass and hissy highs. After a few weeks, I replaced the cap with a Mundorf Supreme. The Mundorf went through a weird series of changes for a week or so, and then things settled in. Plenty of bass extension, but still not quite as "quick" as before, and smooth and relaxed through the mids and highs. Overall, I like the change, but if I was running the amp with restricted lows, as in a "sexy speaker" set-up, I might be tempted to put the old upgrade trans. back in. The pluck of bass strings is a little less distinct.
Bernie