The thing you're forgetting, though, is thateven a 55-watt tube combo is hardly portable. Sure, in comparison to a half-stack plus combo dual rig, it's a peice of cake, but in terms of portability... the 2x12 i checked out was probably in the range of 60-80lbs (great amp, but the presence control on the one i played was screwed up, so i passed).
The selling point of the 55 over the 45 isn't the added wattage as much as the ability to run either 6l6 or el-34 tubes, as opposed to the el-84's of the 45. On the other hand, a lot of the guys artound here prefer the sound of 84's- a little more agressive, especially with the lower wattage. The 45 also has a curvacious/bold switch (i think it's called that- something to that effect, anyway) on the rear panel that i believe is left out of the 55 and 100.
Of course, the 45 still isn't a sack of feathers... I'd say for tone and portability, nothing tops the Tech21 Trademark series. the 10's probably too small for your needs, and the 60 doesn't get super-heavy, for some reason... a trademark 120 combo, perhaps? Sure, it's solid state... but it sounds better than nearly every modeling amp i've played, and a good number of tube amps.