I should add that I had the Cullen mod (now done by W4S) done to my ZP-90 and it made a noticeable difference. Was it worth the money? It's a lot, more than the Sonos itself, but I love the Sonos controlled via my iPad. I wish it were cheaper, but it definitely made a difference and if your Sonos is your primary source, I strongly recommend it after being a doubter for a while...difference was immediately noticeable.