^Time for me to get a feel for the used amp market in that case. Anything in particular I need to look for/be wary of when dealing with used tube amps?
Apple, 50g seeds 420/11
300g chicken, 200g dry red lentils w garlic and frozen veggie mix, 3tbsp sweet and sour sauce. 1400/136
Quark, whey, 100g crunchy. 910/93
2730/240
TDEE ~2500 (short day, 5km walk)
Balance +200
Most good tube amp owners will be able to tell you when the amp was last retubed. When I bought my Mesa Bass 400+ the guy had a certificate from when the amp was converted from US to UK power by a Mesa engineer, and when the amp was retubed at a Mesa service centre (it had all Mesa branded valves).
Now, in the case of Mesa, there are a few extra quirks that you have to deal with when buying - such as them essentially lying about the nature of tubes and pushing their own branded product onto people. You kind of get this with Peavey, as some of their amps have a fixed bias power section, so as the tubes age they fall out of the right range and start to sound shitty. Some of their newer amps have a variable bias so this isn't a problem, but you'll have to break out the multimeter if you buy a new batch of power tubes.
What I did on the Mesa was actually retube the whole amp with a matched set of Tesla/JJ's from Bob at
Eurotubes. If you're unsure about a tube amp after purchase, this is always a wise move, as the tubes are the first thing to be affected by the amp getting knocked in transit etc (they go microphonic and squeal). If you're getting the amp shipped, the tubes should be removed beforehand so you don't have an amp full of broken glass in the mail.
I suggest reading up on Eurotubes about biasing and his tube reviews - Bob has a Tesla/JJ agenda to push and he is US based so I wouldn't order from him every time, but for ease of use you can buy a matched Triple XXX set from him, plug them straight into the amp and get chugging. He is quite helpful via email, especially on aftersale, but the tubes are made in the Czech Republic so you may find a reseller that sells matched pairs/quads of power tubes for less shipping locally or in the EU.
There is a lot of good info on his site about the tonal properties of each type of tube - 6L6 vs. EL34 vs. 6550 vs. KT88 for example.
Other than tubes, you can maybe have the occasional problem with a power capacitor blowing, but any half decent technician can swap these (I've actually done it myself on certain amps where the chassis construction allows you access to the PCB) for not much money.
Lastly, cosmetics such as missing knobs and scuffs on the Tolex are your only concerns. Tube amps are old school engineering and lend themselves to modular and component replacement over long periods of time - my Bass 400+ has been going strong since 1996 through 8 owners of which I'm the most recent, and there are tales of Peavey heads still going 20 years after shipping. Compared to a solid state head, where generally if something fails it takes the whole amp with it, and you're making a more solid investment in the technology.