I agree with Fred. 95% of my music is in Flac. The Sonos supports Flac (and other formats to, MP3, OGG, WAV, WMA etc..)

I use to favour APE but Flac is more supported and sounds excellent. I have very few MP3s and I look to replace them as soon as I can find a lossless version of it.

And like Fred says..disk space is cheap.

Acoustic Zen Adagio, Veritas center, Axiom EP500, QS8s, Anthem AVM20, MC20,Adcom GFA7400