You can buy the DAL-150, which is the device you need to take advantage of HK's MP3 decoding on ebay for about $20 shipped.
I just set it up and it sounds fantastic! One caveate, is that you can't use ANY dsp, and you are stuck with left/right and sub channels ONLY. But, the sound quality is remarkable.
Apparently it's not the greatest prouduct so they must just have given up on it; check out the review on CNET. It works fine for me so I'm happy. This thing used to sell for $150.