As mentioned, the StreamAmp AMP-i50B streaming amplifier is very suitable to build-in, because of its design.
Next to that, it has got a RS-232 port, to be managed in Home Automation / Domotica installations, plus the Phoenix connectors for power and speakers, make this model very interesting for the custom installation market.
With the downloadable app (iOS and Android), you can make the StreamAmp part of a multiroom setup, where you can (re)stream your various music files or online music services, to up to 8 locations within your home network.
That can be many services, such as Spotify, Tidal of TuneIn, but next to that it has also got the possibility to connect USB 2.0 storage devices , like USB sticks or external hard drives.
Or you can use the SD card slot or the DLNA functionality to stream your files from your NAS.
With the included RCU you can manage the volume, power on/off, next/previous file, and invoke playlist pre-sets (max.6), outside of your phone.