The Good: The compact Sonos Amp delivers the company's class-leading multiroom audio to speakers of your choice. The system offers more flexibility other Sonos systems. It's compatible with a wide range of streaming protocols and Alexa's voice assistant. The Bad: Numerous well-featured amps and receivers are available for less money. The Sonos Amp sounds too bright in its default mode and doesn't offer a calibration routine. The EQ settings needed to fix it are located deep within a nested menu system. To use voice, you'll need to have another smart speaker in the system. The Bottom Line: As long as you take care during setup, the Sonos Amp offers enthusiasts a powerful blank slate to build a compact, high-performance audio system. The Sonos Amp is an intriguing product: the company is pitching it primarily at the installers who bought the majority of the preceding Connect:Amps, but it's also very well suited DIY audio and home theater enthusiasts. It is without a doubt the most flexible product the company has ever made. If you asked anyone what they thought the future of music replay was, they would probably say streaming, and perhaps even records. The Sonos Amp can do both things -- providing your turntable has a preamp -- and adds the ability to connect a television. Of course it also works well with other Sonos gear to create an easy-to-use whole-home audio system.The main downside, aside form the price, is that the Amp needs more care in setup than any other Sonos product. Specifically, it's a very bright-sounding amp out of the box, and so requires more careful equalization to sound its best with most speakers. It's not cheap, but with its gutsy performance and thoughtful design, the Sonos Amp should especially appeal to music lovers who relish the chance to infuse their favorite speakers with Sonos' ease of use.So, what is this $600 box all about?Let's back up a minute. If you're not familiar with Sonos -- or you only know it from its speakers, like the Sonos One, or its soundbars, like the Sonos Beam -- you may be wondering what this thing is, and why it costs $600.The Amp is a stereo amplifier that streams digital music, and unlike most of the company's other products you'll need to provide your speakers. It lacks the video capabilities, multiple audio channels, multiple HDMI inputs, displays, buttons, dials and even remotes of a typical AV receiver. Instead it's designed to connect to just two stereo speakers (although some pro installations can connect more than that in a multispeaker mono configuration) and be controlled entirely via the Sonos app or voice commands courtesy of Alexa.Sonos was designed from the beginning as a multiroom audio system. Stick a speaker in your kitchen and one in front of the TV and they can all perform together or individually. While the Connect:Amp this replaces was strictly stereo, the addition of an HDMI port lets the Amp get audio from a TV too, and pipe it anywhere in your house.Design, features and connectionsA component designed to hide out of sight in the depths of an an entertainment cabinet, the Sonos is a small, black unit only 9 inches square and 2.5 inches tall. The top has a curious, circular indentation whose purpose becomes clear when you flip the amp over -- it allows users to stack multiple amps, thanks to a rubber extrusion on the bottom. Sonos does advise active cooling for installations involving more than two amps.The "guts" is the 125-watt-per-channel stereo digital amplifier (8 ohms), which Sonos claims can drive most of the speakers on the market. The amp section outputs to a pair of speaker terminals, which offer the ability to connect either bare wires or banana plugs with a proprietary removable socket.Unlike other digital amps at its price, the Sonos Amp's connections are relatively limited, though it does includes an onboard HDMI ARC input for connecting to a TV, alongside lip synch adjustment. Connect your TV via its ARC port to the Sonos, select External Speaker in your TV menu and the Sonos will playback whatever audio appears on your telly. The amp will also autodetect inputs (TV, analog or streaming) and switch automatically.The amp also includes an analog input for connecting an audio device. You could hook up a turntable for example, and transmit its music around the house, to as many Sonos speakers (or Amps) as you own.While you can pair the amp with the Sonos Sub, the device handily includes a subwoofer out for adding your own sub. If you want to add rear speakers, you also have the option of adding either a pair of Sonos speakers or even adding a second Amp.