It depends in part on what you want the device for.
Sonos has many features beyond just streaming audio. For example, if you are interested in its text to speech capabilities (or a barking dog alert), popular in a home automation system for announcements, @geko has alternative software that runs on a raspberry Pi or old laptop.
If you are interested in the player quality, @ule keeps a list of speaker models confirmed to work with SmartThings you can consider:
And if you want the least expensive player option with very good sound you can get a used 30 pin dock speaker (many of these at garage sales these days) and then buy a connector dongle for under $20.
Anyway, those topics might give you some ideas.
Meanwhile, I’m sure many community members will be able to give you reviews on specific models here, the other links are just to give you some possibilities.
