One thing to think of is whether you want your drive tone to come from the amp or a pedal driving the amp? This way you can decide if you need a twin or single channel amp. As Dad says, 100w valve amp would be ridiculously loud, I had a Fender Bassman ‘59 reissue, which was 45 watts or so and could stun small animals at only half volume! A good place to start would be to look at the tone of folk you admire and what amps they use, that way you can begin with one brand (no guarantee you’ll end up with that brand, however). Interestingly, you name Dimebag as an influence and, IIRC, he used solid state amps. That aside, some the folk you mention favour Marshall amps, so maybe start there.