FYI you can get the streaming url from their public API, you don't have to muck around with string interpolation. They know it's easy to get so they just put it right there in the API for you to use. Also if you used the api you could have your script preferentially download the original file if the artist made it available.

http://developers.soundcloud.com/docs/api/tracks

Ultimately though the stream is a 128 kbyte/s mp3, probably transcoded, and as such you should all feel slightly ashamed of yourselves :)