There is this for MP3:
http://amigakit.leamancomputing.com/catalog/product_info.php?products_id=1078I have one I use (admittedly on my 1200) and it works great.
No reason it won't work on the A500, as the processing is offloaded.
(I think the software needs 2.x or above)..
So a movie player that streamed video and offloaded the audio to the device would be feasible.
You still have some CPU overhead pumping the MP3 thru the serial port, but it should be less that if it processed it thru Paula...
desiv