Very interesting thread :D
I'd also say "get your hands on a modellor".
I'd always assumed (at least 20 odd years) that I'd like "classic" Fenders and Marshall Plexi types.
For the last 5 years or so I've used a succession of modellors (POD 2.0, POD XT, and now Vox Tonelab) - it really opens up your ears to roughly what these amps could do for you, and also what effect speakers might have (stick an AC30's cab on a Blackface, for example).
They are only models, and don't behave like the real amps, but you can get a really good idea and imitate so-and-so's tone off such-and-such record...
Anyway, what it's done to me is this: it turns out I'm not really that fond of Fender amps... I don't really like the Plexi types (and most scary, I don't really like the Marshall master volume beast that all my heroes were using late 70s early 80s, if you gave me one, I wouldn't say no, but I would no longer go out of my way looking for one...).
But I do seem to rather like Marshall JTM types, and Vox amps, once I'd figured out how to use them for what I want to do. I've even ended up buying one of the AC4TV combos on the strength of it...
And the funny thing is, with a single channel, one volume, one tone (and no pedals!), I can get that AC4TV thing to do everything I want, and I can imitate tones that I thought I needed Fenders and Marshalls for :roll:
If you're really interested in finding out, go the youtube route, etc, but also get a modellor. Hours of fun, without breaking the bank or killing the neighbours :D