i haven't heard of any linux drivers that support it yet, but i wouldn't be surprised if it's been added. the cards themselves are pretty new.. if you're interested in getting one, just do a little research on whatever card it is you're looking at. it would also help if you checked out www.kernel.org
- you should be able to find links there that would help you find if there's any support for that feature. and, failing that, you might want to write to one of the driver developers for the kernel. it's usually best not to bother them with most stuff, but implementing mp3 support would probably be something they would be open to hearing about.