I think you could either buy the 2nd Q or do this Pioneer Nav system write up, uses DVD's. It's a 2 piece system which would fit in the Q's Double DIN opening. MSRP $3500.
This system is a little less (MSRP $2700), but requires you to mount the Touch Panel somewhere???
One more Pioneer, but it is a single DIN and would leave you an opening below the head unit. Still pricing MSRP $2200.
This GPS Nav (MSPR $1800)system from Kenwood, the resuires a touch screen to control.
Here's an Touch Screen (MSRP $1300) from Kenwood. Again, not sure where you'd mount??
Here's an In-Dash (MSRP $1200) that "should" support the above.
If you mount the Kenwood GPS unit remotely, you could use this Double DIN (MSRP $1700) to control the GPS.
Or as I said earlier, you could buy a 2nd Q

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