I am looking to add an aux input to my Alpine CDA-9886. I currently am using the high-speed for my 5th gen iPod, but want to add the flexibility of an aux input for my iPhone 4. I am seeing there is an option to convert the CD-changer to an aux input using the 121B, but am also seeing the 236B offers "high-speed aux in." Does this mean anything in terms of sound quality? Will the sound quality be better on the KCE-236B versus the KCA-121B?

Thanks in advance for your help.