I misunderstood your initial post...I did not think you were very aware of Sonos. If AirPlay works for you, then you can create a full home system with AirPlay as a foundation.I've had a play:1 for 2 years using the Sonos app, I'm very familiar with it. It's nice that it can connect straight to the NAS, and I can just hit play when I come home and it will pick up where it left off. In the end it just collects dust since I'd rather just open my iTunes and hit play to airplay some music.
As a side note of interest, check out the new Google Chromecast Audio adapter that was announced this week for $35/ea.