About one year ago I listened to the Clase CA 151 in comparison to the Classe CA 150. I could discern no appreciable difference between the two. I also happen to like the cosmetic styling of the older CA series better than the new series. With that being the case, I purchased a CA 150 used here on the AudiogoN site and paired it with a Classe Six preamp also purchased used through AudiogoN. The Six is sonically superior, IMO, to its predecesor, the Classe DR-6. I believe the excellent quality phono section alone on the Six is worth the preamp's value used. The older series Classe gear has been reviewed in many of the audiophile publications. These reviews can frequently be found in the product archives on the publication's (Stereophile magazine, etc.) websites. They might provide a starting point, or frame of reference, for comparison. Trust your ears, and good luck with your own comparisons.