It sounds like you've done your homework on finding a well built receiver with all the features you need. Good job. Perhaps better than you know.
As for that power issue, in the real world there's virtually no audible difference between 90 and 100 watts. In fact, to make a barely audible difference you need to double, or halve, the power. So, if you were "satisfied" with the power of your current Sony, you won't feel any loss here.
But wait, there's more.
The way receivers are marketed, as you go up the chain, power isn't the thing you should be looking for. You should be looking for the features you need. As you noticed, going up the chain, the power ratings really don't change too much, do they? ...but the number of features, inputs, outputs, etc, do increase, don't they? If you wants gobs of power you really have to invest some serious $$$ into a receiver, as you may have noticed.
Well one of the "features" that Yamaha has is preamp outputs. This allows you to add external power amps to that receiver and still use it as a control center. That's the most economical way to get the features you need and the power you want.
So, get that Yamaha and enjoy it. If you ever feel the need for more power, and nobody would fault you, there's a plethora of power amps out there just waiting to fill your needs.