Audio-only -- but that's a good thing
Unlike some of the more well-known media streamers on the market, the Sonos devices are audio-only, no video. While that may seem limited in scope, the Sonos is more about focusing on doing one thing as well as possible.
Sonos' tagline is "Stream All The Music On Earth" -- and the company's products come very close to that goal. The Sonos is compatible with nearly every popular music service: Mog, Pandora, Spotify, Sirius XM, Last.fm, Slacker, Rdio, Songza, TuneIn Radio, Rhapsody, iHeartRadio, Wolfgang's Vault, Aupeo, Stitcher, and -- most recently -- Amazon Cloud Player.
For those keeping score, that's nearly every cloud music service out there. And while, as mentioned above, Apple's iTunes Match isn't supported (thanks, as always, to Apple), the Sonos does support streaming from PCs and Macs running the iTunes software, so your home music collection is always accessible. It also supports many NAS servers, for those who don't want to keep their PCs powered on all the time.
For local music, nearly all popular file formats are supported: MP3, WMA, AAC+, Ogg Vorbis, WAV, AIFF, Apple Lossless, and FLAC. That said, while it will only concern a small subset of people at present (myself included), the Sonos system doesn't play back high-resolution 24-bit files: it's CD-quality only.
Totally wireless -- with one caveat
The Sonos family of products is designed as a multiroom audio system, and connect to one another via a proprietary wireless mesh system. The advantage of that is that it's not limited by your home's Wi-Fi network. The drawback is that there needs to be at least one wired connection between your home network and a Sonos unit. (Think of it like a DECT cordless phone system: one base station needs to be plugged into the wall jack, while the others communicate with that one wirelessly.)
That gives you two alternatives: you can situate the first Sonos in your home near an Ethernet connection, or you can buy a $50 Sonos Bridge.
Like any hi-fi system, the performance is mostly dictated by the speakers you use. When using the Connect:Amp I got the best results from the Intimus 4T Tower Speakers with a sparkling treble underpinned by detailed mids and tight bass. Sure, you could spend more on a dedicated amplifier, DAC, and music streamer, and get better-sounding results, but it would a) cost a lot more and b) lose the cohesion and convenience a one-box system offers.
Whether it was playing music offered by Spotify or from a local NAS, I enjoyed glitch- free playback from the Connect:Amp and there wasn't a hint of lag time. This was especially important when connecting a TV, and I found there weren't any sync issues despite simultaneously streaming around my apartment. The only thing to keep in mind is that any line-in signal is converted to digital, and when I hooked up a Pro-Ject Debut III turntable I found that the sound was more restrained than when connected to an analog amplifier. As such, I would class the line-in as more of a convenience feature than a true "hi-fi" consideration.
As far as other speakers were concerned, I also had good results with the laid-back B&W 685s, though when compared with beefier amplification the bass was a little lean. Listening to "Life" by The Beta Band, I felt the system wasn't as capable in relaying the bass synth outro (2.36), sounding a little more reticent than my Marantz receiver. The amp was able to drive the speakers to party levels quite easily, though.
Not all speakers were as successful, and it was surprising to find one of Sonos' to be less than exemplary. Adding the Sonos Sub, I found it didn't boost the midrange performance in the same way it did with the Play:3. The inability to set a crossover from where your speakers' bass performance tails off also meant you couldn't tailor bass response. A third-party sub from the likes of HSU or REL for the same $699 price or cheaper would give you more flexibility and better performance.
While I found the software quite easy to use, it did have some niggling problems that competitive systems don't have. Firstly, the "sort by folders" option in the software doesn't read folders that haven't been indexed yet, and you need to reindex (but not on the fly) to find recently added files. Secondly, and quite irritatingly, it's very easy to bump the app's volume slider up to ear-splitting volumes. Thirdly, Spotify integration could be better. I was really taken by the Squeezebox Touch's take on the software, which enables users to use it in much the same way as they would use normal Spotify -- starring items and editing playlists, for example. In comparison, the Sonos is limited to reading playlists and starred items. It's also difficult to play a starred album, as the Sonos is set up to play individual tracks generally, and so the continual playlist nature of "starred tracks" means playing an entire album is problematic.
That said, the Sonos apps are updated several times a year, so anything one may object to currently may well be corrected in a future update.
In my reviewing time I used both the Connect:Amp and the Connect, and when switching back to the Connect I found I missed its bigger, amplified brother. Building a system around the Connect:Amp makes a lot of sense if you're starting from scratch, and the total app control makes it much more compelling than the Connect -- where you'd need to separately turn on your stereo and flip to the correct input before enjoying the music.
There are plenty of cheaper alternatives to the Sonos Connect:Amp. You can stream audio from a smartphone or tablet app to any Bluetooth speaker or a Bluetooth dongle like the Belkin Bluetooth Music Receiver; but Bluetooth sound quality will leave critical listeners wanting.
Another alternative is to connect an Apple TV ($99) to any existing stereo system. The Apple TV supports all of the Sonos services plus iTunes Match, and you use an iPhone, iPod Touch, or iPad as a remote. But with the Apple TV, you'd have to flip between a dozen apps (using AirPlay), rather than using the all-in-one Sonos control app. And -- unlike Sonos -- it's not useful for Android or Kindle Fire owners.
At the end of the day, the Sonos Connect:Amp isn't cheap, but it's a better no- compromise digital music system than those alternatives listed above -- especially considering Logitech has discontinued its Squeezebox range and replaced it with the UE Smart Radio. If you're serious about your digital music -- and about cloud-based music services in particular -- the Sonos Connect:Amp is a tidy all-in-one system.