When I first upgraded to a higher-end system, I heard how unforgiving it was of poorly recorded cd's (mostly rock). I tried the Auric Illuminator (AI) and it definately improved the sound. Quietier background and smoothed out the rough edges in the high range. The treated cd's sounded really good in my auto's cd player. The AI isn't a magic solution for poorly recorded cd's, but it made them playable again. And I appreciated that.
