Amplifier Weight. A Factor?

Absolutely! I sold a KR Audio Antares even though I liked the way it sounded because it weighed 90 lbs and I was sick of lifting/moving it! I went with a succession of nice tube amps in the 30-50 lb range. The thing about heavy amps, tube amps especially, is they're not just heavy but awkward because of how the weight is distributed. SS amps often have handles but tube amps almost never do.

Everything else being equal (and in reality it never is) the reason that large amps are very heavy is they have very heavy transformers which you really need to get high quality power and things like subterranian bass. If you can settle for less power, and don't need really deep bass, you're less likely to get a hernia. I have both heavy monos and a lite 35 watter and for the power I need the only real difference tonally is the impact in the bass below 30hz. FWIW YMMV.

Although you need big and heavy transformer to have true high power output, it is difficult to handle. I sold my krell 700 cx because of that and go for Nagra VPA.