Not your everyday bookshelf speaker?

I love my LaHave Mela monitors. I have posted about them in the forums here.

You might want to take the line out from the Sonos and run the line level signal into a powered monitor. (This preserves the "hands off" automation of the Sonos, since these are usually signal sensing, auto-on devices). IME, this can be a high value solution for improved SQ via Sonos.

Powered pro monitors usually offer great value, if you can live with a plain cabinet. I use the M-Audio BX5a in my kitchen and get great results for a $200/pr investment. KRK makes a similar series of products that are highly regarded. You can find improved cosmetics at a higher price from home audio producers like Quad and Paradigm (discontinued, I believe - but likely available used).

I think that NHT still makes a reasonably priced option and Audioengine's offering has been well received by some here on A'gon.

Good Luck.

Marty

Reference 3a makes some excellent stand-mount speakers that are very efficient. Not cheap, but high value.