I bought the $50 version and use the little DAC that comes with it. I bought it at Circuit City thinking I could return it if not satisfied. It was a no-brainer to keep it. Instantly I knew it sounded better than the y splitter cable I had been using to connect my computer speaker output to my aux inputs of my stereo. Yes, better bass and more musical.
The $100 version looks light it comes with a little more substantial DAC even though it's probably the same chipset. Would get better fidelity using your Cary dac? I don't know. Just buy it somewhere that has a good return policy and play around with it. There may be other solutions, but this works well and was easy. I have a home office and listen all day long. Good Luck!