I hear you 2out2sea. I've done my share of buying and trying and re-selling at a loss. Sometimes it is the only way to go if you want to demo gear. Are there any Jolida dealers near your or an audio society where other members have various amps for you to audition? If I lived close to you I'd lend you tubes to try in that Jolida 502B. Hmm how about buying some power tubes or preamp tubes for your friends Jolida to try and tailor the sound to your liking. The re-sell of tubes isn't as bad as re-selling amps. It is a lot easier to re-sell tubes than gear IMO.
Best of luck with the search.
Best of luck with the search.