I do have spares but I’ve had poor experiences purchasing tubes over the years already. Had a brand new power tube fail within a month or so. And a NOS Black Treasure flare up and die the first time I plunked it in. With these being matched pairs, it makes it harder to find another spare. I’m also finding the sound just doesn’t seem to be 100% consistent day to day. I’ll sometimes get flutter or static here or there, slightly shifting soundstage or things are good for a week at a time. Now days I’m having a hard time taking off my analytical hat and just being able to enjoy the music. And troubleshooting a pre amp/amp with 11 tubes in the system just doesn’t tickle my fancy any more and as they age it won’t get much better.I get all of that!
Here are a few tips that makes this all go a lot easier!
1. Always buy tubes from a source that allows you to return them if defective.
2. As soon as you get the spares, run them in the system a few days to make sure they are good; then set them aside since they are spares. Now you know they are good.
3. If a channel acts up, the first thing to do is to swap the interconnect cable left for right going into the amps. If the problem moves, its the cable or the preamp. If it does not, its the amp or the speakers. Swap the speaker cables at the back of the amps to determine the latter; if the problem moves its the amps.
4. If you've sorted out what bit of equipment has a problem, then swap the tubes left for right and its pretty easy at that point to sort out the bad tube.
5. You can knock on tubes to find out if they are a source of static or microphonics. Some tubes can be so microphonic that rubbing them gently on the top is more effective.
I'd like to say that you can find a solid state amp with the smoother more emotionally involving nature of tubes, but so far that has yet to be the case. I know you've had a lot of suggestions here and some are pretty good, and those amps will probably have tradeoffs with the one you have now. But if you find that they just don't have that 'something', that 'something' is probably emotional involvement with the music. This happens when the brain processes music in the limbic centers the way its supposed to- when things go awry then it processes music in the cerebral cortex and the emotional connection is vastly reduced!
The main reason we lose that emotional connection has to do with distortion- tubes make far less of the distortions that the ear/brain system finds irritating (and also uses to sense sound pressure). Transistors make more of these distortions (higher ordered harmonics)- that is why they tend to sound brighter, even though on paper they have flat bandwidth...