Ahoy there!
I couldnt afford to buy the factory-gps-system too, so I did bought MIO A701 and replaced my mobile phone with it

one for all (cellphone, pda, gps).
GPS reception inside the car is very poor because of the thermal glasses. But there is an area on the top of the front glass, very close to the mirror, where you can see that the glass is painted. In this area, there is no thermal protection of the glass and this is for receiving like GPS or TOLL machines etc.
MIO A701 comes with a base that sticks in the glass securely. So I have put this base under the mirror. There is a perfect reception there and when I enter the car, I just put my cellphone with gps in this place. It works perfectly and also I do have a way to speak to the phone, because when there is a call receiving, I just press the speaker button
cheers
Minas
Minas N. Miliaras
Athens, Greece