HDP6 Passive Speakers (Open Box)

Absolutely!  You can connect any Audioengine speaker with an analog output to any Sonos product that has the Line-In feature.  You can also connect any Audioengine passive speakers into an existing Sonos system using the Sonos Amp.

The lower the speaker impedance, the more current (amperage) your amp or receiver will need to provide, but most separate power amps have more than a sufficient power supply and power amp sections for driving 4 ohm loads with ease. In fact many amps will perform better with a 4 ohm load as opposed to 8 ohms if their design is robust enough to supply the extra current. A quick web search will bring up more information on this subject.

The HDP6 is a very efficient speaker and designed to work well with digital hybrid amplifiers (Class-D, Class-T, etc.) as well as most stereo receivers, integrated amps, tube amplifiers, and whole-house music systems such as the Sonos ZonePlayer 120. The HDP6s have an amplifier power rating of 10-150W per channel, so any amplifier that outputs that power should work great!