An entire genre of music might be called “hidden-treasure rock” and it would be made up of those bands that, when you stumble upon their albums in record store racks, you feel like you’ve won a prize.

We test plenty of Bluetooth speakers in the $100 range, but few of them are stereo systems with dedicated left and right channels. The Logitech MX Sound, at $99.99, offers both wireless and wired ...