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Other then Onkyo, is there a AV receiver with air-play built in that supports spotify?
Not too sure if it's along the same lines, but the Philips Streamium range - though I imagine this is closer to Sonos than the Onkyo.
I have an Onkyo but it doesn't support AirPlay. I bought an Apple TV and connected it via HDMI to my Onkyo. I can stream from Spotify App on my Mac, iPhone and iPad with my premium account and it works really well.