Amplifiers don't deliver sound; speakers (drivers, cabs, whatever...) deliver sound. Watts is a unit of power, not volume; decibels is a unit of volume. The more efficient the speaker (driver, cab, whatever...), the more volume (decibels...) it can deliver for a given power (watts...). This would be referred to as its 'efficiency'. Soooooo... A low-powered amp into an efficient cab can produce more volume than a high-powered amp into an inefficient cab. Watts, in themselves, are a very poor unit for expressing volume.
What's the solution..? If volume is required, look for an efficient cab, then match an amp to that cab. Turn the volume down at home. There is no contradiction; a good amp/cab combination can be used on stage and at home with no issues. If arena volumes are required, the PA will do the 'heavy lifting', anyway, and an IEM system will keep the stage volume at decent levels, whatever the amp/cab. Any quality amp and/or cab will be fine for both purposes (but a less imposing version may be preferred for home practice, to avoid carting stuff around...)
There's a lot of advertising spiel surrounding the selling of music gear in general; don't be taken in by claims of 20/200/500/1000 watts or whatever, and ask your peers for their experience of 'real-life' usage.
Hope this helps.