Welcome! I have the exact W-series arrangement you plan on getting, you will not be disappointed!

I also use Sonos and highly recommend it for the very reasons you mention. As you already know, Squeezebox and Airport will do most of what Sonos does, so it's all about what's worth it to you. For me an expandable system that can play different songs in different rooms was the selling factor for Sonos vs. the other systems (plus my wife surprised me with it for Christmas)!

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1