I have found it usually doesn't really matter... For regular home use with most (but not all) home speakers, a Yamaha or Denon or Onkyo will all be fine. Sure, they won't be outputting true 100 W/ch on all 5 channels simultaneously, but that's not necessary for most people.
One brand that is noticeably less powered than the above in real-world use is Sony. Ironically, I own three Sony receivers mainly because they were the cheapest at the time, with the desired amount of inputs, and even for my main home theatre (Paradigm Reference speakers across the front), they are sufficient. At the time, if you wanted a Yamaha or Onkyo with more HDMI inputs, you'd have to go with a physically larger and more expensive model, whereas with Sony you could stick with a lower end inexpensive model that had a smaller footprint... hence the lower oomph output.
I have noticed no audio difference going to a cheap Sony receiver. However, I could see it becoming a problem even with regular home use if you have really inefficient speakers in a large room, and you like to crank it.
Note however, most of my bass is separately powered. My SVS PB13-Ultra has a built-in amp of course.