Admittedly you don't need much power for a lot of sound. But (and this is repeated countless times here,) there are many variables. It's hard to say what's going to work for any particular person.
In my bedroom system, I manage with a Yamaha series 800 receiver (never remember exact model.) It lacks power IMO, IF you want to crank some music. I feel like higher end Yamaha receivers do music better, because you don't hear that harshness at the higher volumes I might (occaionally use) when cranking music while cleaning or some such.
With efficient speakers, and if you don't need a lot of SPL, you will hear people getting by just fine with a 5 watt tube amp. Admittedly tube amps are reputed to clip more pleasantly (probably why they make good guitar amps right?)
100 honest watts seem good for almost any reasonable needs based on years of me reading up on audio. But you will find a lot of people coming into these forums are not reasonable. They want near reference level or reference level SPL. That's in a different ballpark than reasonable. You need to double power for each 3 SPL sound level gain, which quickly raises the money you will have to spend (and not just for your amps, you really need speakers and sub(s) that can hack it. (NOTE : I am not putting the reference level people down, just saying they would not fit into my catefory of "reasonable" needs ... high performance fans in all areas are always a fringe element, such as auto hot rodders/tuners, PC overclockers, etc...I am one of those unreasonable people myself sometimes.)
So like I say, it varies a lot and answering the question 'worth it', one of the most ambiguous questions asked in forums, is not easy.
Based purely on my own experience, I like high end Yamaha receivers. Like $1500 MSRP or more. Seems like they don't run out of power like the lower systems. When I added amps to my system, I did not notice a big improvement (note I run my volume at least 10 dB below reference, so again, your milage may vary.) This flies in the face of people saying you only need a few watts of power. I can only speak from my own experience, other people may have different experiences.