I fitted a Joying 7" one, didn't have to do any of that extra moving switches, just slightly bigger than standard double din size so fits right in to the 2 top slots but needed a little trimming with a dremel to fit the bezel.
It's pretty easy to do yourself, there's a few YT videos and instructions kicking around, just need to get a double din kit, e.g.
EURO MOTORSPEED 97-02 PORSCHE 986 BOXSTER DOUBLE DIN INSTALLATION KIT | eBay
CT23PO02 Double Din Stereo Fascia Fitting Kit For Porsche 986 Boxster 1997-2004 | eBay
and this new one that comes with the some weird lower dash bits built in...
Metra 99-9605B Single/Double DIN Dash Kit for Select 97-05 Porsche 911/Boxster