In a retail environment, it's best to fill the space evenly with sound, so you want to consider that. One speaker playing in an obvious location brings to mind dusty radios on file cabinets. If you use only one, position it carefully, and make sure it's got the meat to play quietly and clearly at the same time.
Before you buy anything, see if you can bring in an audio source and position it around the space while listening. Doesn't matter what it is. You should be able to tell if one speaker will be sufficient rather quickly. Clothing is good in relation to reflections, but too much insulation in a space can impede performance.
If you're good with one speaker, Sonos is fine. Bose offers similar products, and so do others. You might want to stick with those two, though, for the greatest compatibility, simplicity, and support over time. What I'd put in a retail establishment is much different than what I'd put in a home, and there are lots of neat little options out there that will work well.
Bose is more simple to expand to multiple speakers than Sonos, but Sonos is more easy to control with mobile devices. Six one way, half-dozen the other. Whatever you do, keep it simple. You don't want to keep having to screw with it in a business environment. If you can get away with a single speaker, do it; and pick a primary music source and stick with it.
Don't try to do too much.
The legality of what you play and when you play it is a different matter, and best examined personally as it pertains to the scope and recognition of your business.
Also, note that Best Buy has a pretty bulletproof return policy; at least 15 days. I get 45 as en Elite Plus Rewards benefit. It ranges a bit, but however long you have, they don't hassle you. If it's not working for you, bring it back and try something else. Don't be afraid to just give something a shot.
One more thing: Make sure EVERYONE that matters can use it.
Cheers,
Kennith