The problem is that the same exact tube will behave differently dependin on how you run it.
Run single-ended, push-pull or OTL, and it'll sound different.
It'll sound different whether you run negative feedback or not, and also depending on how much feedback you use.
It'll sound different whether you use a solid state rectifier or a tubed one.
It'll sound different depending on the voltage the tube is biased at.
Unfortunately, there aren't any yes/no answers with tubes. The good news is that there are lots of variations and sounds, you can build all sorts of interesting new designs.
Instead of focusing on the superficial characteristics, look up the various topologies, how power supplies work and look at some tube datasheets to see the effect of changing the bias. There's a lot more to this, but get the basics down and don't worry too much the rest. Average tubes in a great circuit are a whole lot better than running rare old NOS tubes in a lousy amp.
There are a lot of great, free, texts over at pmillett.com. Start with Norman Crowhurst's books - very accessible for anyone without a technical background.
