Have a look around, there's plenty of info on here.
Personally, I'm using a Genz Shuttle 6.0 head and Schroeder 1212L cab which, combine,d comes in at around 58lbs and could go louder than my guitarist who has a 120w Peavey 5150 which weighs as much as a small village if I needed to.
Once you've had a look, you'll realise that it has little to do with watts and more about how efficiently your cab can convert the power to sound