In case you all are still interested.
Here is the reply from Mark Levinson (Madrigal)
Thank you for sharing your comments on the performance of the Mark Levinson system installed in your new GS300. We're not aware of an aftermarket solution for playing MP3 through the system. However, Lexus has a Customer Satisfaction department that is set up to address all connectivity questions for the systems in the cars, including our systems. They might have some additional advice here. You can reach them at 1-800-255-3987, Monday through Friday, from 6:00 a.m. to 5:00 p.m., Pacific Time.
Happy listening (and driving),
Todd Sutherland
Madrigal
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