Considering the cost of the factory system, I'd go with a replacement stereo that has the flip up screen for navigation. They cost $1200-$2500 installed depending on the brand and quality.
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1987 928S4 Silver Metallic (980)/Navy (TP) 5-Speed
2000 Boxster Speed Yellow/Black 5-Speed
1966 Wife White/Brown Top
1986 Daughter White/Brown Top (Sold!)
1992 Daughter White/Blonde Top