I picked up a Zu Birth on Ebay this past summer for pretty cheap, the seller is zupromos and they always have stuff up for sale. That being said, it's built well, is flexible, and is better than a stock power cord.
However, if you're really unsure about the purchase, why not minimize your risk a bit? The Volex 17604 power cords (
www.Carlton-Bates.com sells them) are dirt cheap and seem to compare well against other sub-$100 power cords.
Give it a shot, and if you like what you hear, then maybe get something a bit nicer granted the rest of your system warrants a ~$100 power cord

edit: Are you using your iPod as the source?