This is very much a 'first world problems' discussion, but my pennyworth is from the perspective of someone who owns both S/S and - very recently - a valve amplifier. I've always had S/S, from original Quad 303 through (currently) Mark Levinson 331 and (my favourite) Michell/Trichord Alecto II monoblocs. All lovely stuff and I've never felt short-changed in the music department, but I've always been curious about just what difference (if any) a good valve setup could make.
The first valve amp I really listened to was an Octave v80SE, at the dealer from whom I was buying some Martin Logan speakers. Was most impressed but, in a dealer system, hard to tell what was making the difference. But it whetted my appetite – valve-curious, if you like…
A couple of months ago, having missed out on a great deal on an ARC i50, I got the offer of an Octave v110SE with the add-on SBB capacitor bank, at price which, had I turned it down, I'd have spent the rest of my life kicking myself about.
So, inserting it in place of the Arcam pre and Alecto power amps in my system, and I'm absolutely delighted: there's an inherent musicality, subtlety and depth to the output that was (and remains) immensely appealing. That's not to knock the previous system, but just that the Octave provides an overall more satisfying experience, and I find myself listening to music even more than before, and finding new things to hear in familiar recordings.
The downside of course is warm-up time - I've been listening for about 40 minutes this morning, and the thing is only just waking up and getting into its groove.
Then there is the cost of replacement valves, but you factor that into the purchase anyway - I'm actually pre-emptively purchasing a new set of KT150s against the time when the in-channel supplies of Russian manufacture dry up altogether.
I'm also discovering the delights of 'tube rolling', which adds yet another geek dimension to a thoroughly OCD hobby… :-)