I now consider that question resolved.
I am starting to have second thoughts about the double DIN thing because it requires relocating the a/c controls, causing the loss of the lower storage tray. Because I have the Boxster Red interior I don't want to just insert a black replacement where the CD storage is now, that won't look good. And the cost of a red leather tray is astronomical.
I don't really need a large display but it does update the car's look by 10 years. And I cannot find a single DIN unit that has built in BT streaming, iPhone support, USB playback and does not look like a Christmas tree.