For better funtionality and sound, you can connect them to Sonos (Sonos receiver & your hifi, or just Sonos speakers).
Sonos are working with Amazon to make the systems integrate properly in 2017 (possibly early).
Only the Play 5 (the big one), as it has line in and the 1 and 3 don't. At least that was my understanding from a quick read earlier this morning.