Re: When someone says an amp sounds modern...
How about the Vai's and Petrucci's of the world? I think they have pretty modern sounds from modern amps. Modern to me is tight and crisp, more gain than you'll ever need (I never go past 12 o'clock) and solid thump in the bass and a sound that can be fizzy if not eq'ed right.
For all the negative aspects of bad modern amps, there are equivalent setbacks for bad vintage amps, not enough gain at low volumes, flabby bass...