Rockbox can play FLAC and OGG files. It is very configurable. You can choose how your music/book are filed. I have never heard any incident of the DRM capabilities of stock OS being harmed by Rockbox. You can switch between stock OS and Rockbox easily. It does have a bit of a learning curve and is not for every one. I am an avid Linux user and love to tinker with all things digital. Comprehensive manual here:
http://download.rockbox.org/daily/ma...box-build.html