My suggestion to those who have unknowingly purchased a watermakred disc and think the sound has been impaired, is to return the CD to the place of purchase and demand a full refund. Follow-up with angry letters to the retail owners (if a chain), the record manufacturer, the recording artist and your Congressional representative. Be pro-active.
BTW, the watermark system is easily defeatible by computer users. The goal of watermarking is to have a disc that plays perfectly on a normal CD player, but produces errors on CD-ROM drives. If someone has a CD player with a digital ouput and a computer with a soundcard with a digital input, then the watermarking will be by-passed.