Hey there,

I know its a little time consuming but I think that you should rip your CD's all over again and make sure that you convert to WMA. I wouldn't recommend doing this from your mp3 format because I'm pretty sure you'll be sacrificing the fidelity of your music -- It would be like making a copy out of an already inferior copy. What bitrate are you encoding at? The 650 WMA estimation could be based on a bitrate of 128 or perhaps even lower. You should be able to get good sound quality if you rip at 160 or 192. WMA's also draw more power than MP3's, so there's a tradeoff there.

You can probably get a more detailed answer if you post this question at www.z5lounge.com. Its a site that is dedicated to the Z5.

See you there!

Slydini