A popular mod for boxster owners is to move the heater control unit down to behind the gear stick in order to fit a double din radio. There are many kits on ebay you can buy to do this. The centre trim where the control used to be needs a little tweaking. You need to cut away some plastic in order to slid the double din head unit in. I bought a conversion kit a while back but wasn't happy with it. The reason was, when the double din radio was in place, there was a gap between the top of the radio and the surround (just below the air vents). I put the project on the back burner at the time.
I was going through things last weekend and started to think about this again. Normally when you lower the heater controls, in the space above you have a storage bin (for phone etc..) I needed to buy this as in the place before was a CD rack (which I wasn't going to need). I found on ebay another conversion kit that included the storage bin and surround for the heater controls all in one, plus the radio surround for about £70.
Also the surround for the radio is better as it fills the gap I was talking about and you actually screw the radio to the surround, so no need for the metal cages that most radios slide into. I mocked up the fitting and was really pleased. The new kit was matt black but I plan to spray this satin black so it matches with the rest of the interior.