My memory from decades ago is of research compiled into an AES paper I can no longer access (let my membership lapse since my career took a different path). The result was the peak-to-average power ratio for music was on average 17 dB, a factor of 50x in power. Modern results I have seen online point to far less than that for highly-compressed music, but about the same for well-recorded "dynamic" music. Movies have been shown (various threads mainly on AVS and other anecdotal evidence reported by folk using various SW tools) to exhibit 20 dB to as much as 30 dB, power factors of 100x and 1000x respectively, but since most of the highest peaks were for things like gun shots and explosions I am of the mindset that I can stand a little clipping for those scenarios.
It's been my experience that people tend to greatly overestimate their average power needs and underestimate the peak needs, though it more or less works out. People who think they need 100 W and discover they are only using 1 W on average, have the headroom they need (20 dB) for almost everything with that 100 W amp.
At least in the midrange; more power is generally used in the deep bass so you can "feel" it.
And people tend to neglect the issue of whether the speakers can handle the power, and how much distortion they generate.
For me personally, 80 dB is very loud, so creating a system that can meet the THX etc. guideline of 105 dB per speaker (and 115 dB for subs) is more (way more) than enough dynamic range for me. I tend to focus on the lower end of the scale by building a well-isolated media room that is nice and quiet rather than getting enough speakers and power amps to liquify my body.
All IME/IMO/FWIWFM/YNNV/etc. - my 0.000001 cent (microcent) - Don