Same watts at 8 and 4 ohms?

Elliott, thank you for the thoughtful response. I will take it all into consideration.

However, right now and against the prevailing wisdom here is what I am going to do and why.

I am going to order the Sonos Amp for my birthday next month. Here is why:

Class D, 125w into 8, 200 into 4 and "4 ohm stable" for whatever that is worth. Right now I'm satisfied with 75w into 8 from an old Onkyo AV unit. The Sonos AMP will be a step up from that I suspect. If so I can live happily with it.

It is small, runs cool, nothing else will need to be attached to it since I can ditch the Sonos Connect and use it elsewhere. That means it will be discrete and out of sight and make my wife happy and be controlled entirely by my cell phone or hers. And that is important! She will use it if it is no more than using the Sonos app. And if she uses it then there is buy-in and that is good.

It comes with a trial period with free return shipping so no risk if it turns out to be a huge mistake.

It has balance, simple EQ and fairly effect "loudness" switch for low volume listening. Even with the Onkyo and even at low volume the bass via Sonos with loudness on sounds very pleasing to me.

If the Sonos Amp plus the Aerial 6Ts just don't work out I can try the Aerial 5Ts plus the JL Audio sub with the Sonos Amp but I would rather not since I'm not fond of subs and that is more room clutter to make my wife unhappy. The 5Ts and the sub are still for sale right now.

Sounds like a reasonable plan to me.  Please do report back on the outcome.

When a manufacturer claims x Ohms stable, all they are saying is that the amp won’t start oscillating (and perhaps blow up) when presented with such a load. It does not suggest how it will otherwise power, perform or sound into such a load. 

I'm good with the not blowing up part. That's a feature that I find reassuring. ;-)

Also, from what I am able to understand from this thread is that since I am not likely to ever use more than 50% volume and usually around 30% I should not be taxing the amp to any degree.

The Onkyo does not get any warmer than would be expected at these volumes.

Bottom line: If it sounds worse than the Onkyo then it goes back to Sonos at no cost and falls into the live-and-learn category.

I do understand that this amp is beneath the 'dignity' of these speakers.  And it does bother me a little bit.....I don't know why. Kind of like putting Prius tires on a Ferrari. It would still do a lot of what a Ferrari does well....but not what it does best.

And I don't want to sell the speakers. They cost me nothing and one of these days I might find an application for them in which they can be driven properly.

Don't know about the sonos but nowadays don't most amps go into some kind of protection mode before blowing up.?