DIY: USB audio line out?

Just a thought to share - (as i 'study' for my physics test) i stumbled on this page
http://www.ibhdoran.com/usb_link.html#SiliconAudio

and started thinking about the possiblity of making a USB D/A converter.

Philips has some circuit diagrams and other good stuff here http://www-us7.semiconductors.philips.com/pip/UDA1335H

So how much work would this be?
so where in there there is mention of firmware (don't think i'd be able to handle that one)...

You can buy these things if you look hard enough. Here's a review: http://www.dansdata.com/usbspk.htm

If you were going to make the thing yourself, you would also have to write a driver.

Chris

Cool.
But where do i find one ?