DAB on a convertible 2007 XK

Your thoughts on after-market DAB/AUX radios would be appreciated please. 

I have an MY2007 Convertible XK and want to add DAB /Aux In. I am thinking of fitting an after market DAB receiver with auxiliary in (so that I can play from my iPhone) and am thinking of the following device :

http://www.dabonwheels.co.uk/Kinetic_digitizor_DAB_DAB_plus_DMB-A_car_radio.html

Before I buy, I am keen to understand the likely signal quality I will get which is influenced by the aerial ;

- how well will a glass mounted aerial work on my car ? Is the glass heat reflective ? Will this, or the heater element get in the way of the signal ?

- I have no roof or rear window to mount to

- I do not want to fit a body mounted aerial

- I could fit a converter to allow the DAB to hook up to the existing aerial in the rear spoiler, but I don't know whether that existing aerial is amplified or not

If anyone can help me with the answers to any of these questions or thought, I would appreciate it. 

Thanks

Geoff