On amplifier power
How much amplifier power do you need?
There's no rule of thumb that'll work for everyone... If you need more cleans, and especially more bottom end in your cleans, you need more power. If you want more power-stage distortion, you need less power. But there are no absolute numbers.
The power you need depends upon how loud you need to play, where you set your tone controls, whether you get you distortion by overdriving the power stage vs. using a master volume or pedals, how efficient your speakers are and how many, closed- vs. open-back cab, room size, number of people in the room, style of music, etc.
That said, a doubling or halving of power (a 3 dB change) will make a noticeable difference in how you fit into the mix, all other variables remaining constant. Some people think 3 dB is "just barely noticeable". Put a Hot Plate on your amp and change the attenuation by one click (4 dB on the Hot Plate, but it's close enough) and notice how big a change that really is.