Re: Variation of Amps
Yes and no......
No and yes.
There are incredible variations in both. And there is no global measuring scale.....nor perhaps any real need to try and invent one as its not really something anybody is really interested in specifically finding out.
Most of the actual practical use for this area comes when you consider that the amp is the ultimate link in the tone chain (and i'm talking amp+speaker+enclosure here). In many ways it is the most critical aspect - a poor choice here will essentially 'negate' any awesome components preceding it. And a great amp can sometimes 'rescue' a bland guitar, pickup set or effects.
The best, of course, is to have good components throughout the chain. Then, the myriad of pickup choices will sound just as distinct as they can be.