Ulpian - I don't agree at all with your opinion - there is good few people around that fitted double din radios with sat-nav with 6.1-7 inch screen and it looks amazing.
Fitting that kind of a device is not that hard!
Fiat Connect Nav+ built-in satnav system is not worth any money - it's very old system with only 256colour screen not even able to have a reversing camera attached or dvd-video playing facility. I was thinking of getting it when I've been ordering my Bravo so I asked for any details about it - I got the original manual for it and after studying it very carefully i've realised that it's not worth it.
People have fitted Pioneer's double din models aswel as Kenwoods DNX models, even DNX-8220BT - which in my opinion is the best. Why? First of all Garmin navigation system which i find as most reliable sat-nav system after testing out Destinator, iGo, TomTom(which doesn't have the greatest maps!). Garmin map of Western Europe 2010.10 is the best I've used and that map can be used in kenwood devices as they have a Garmin sat-nav system. You don't need to go for 8220BT model - you may go for something cheaper (7220,5220). Kenwood has also Double din dashboard adapters for different cars and adapters for steering wheel controls. Search the forum for Bravo 2 DIN for more info.
Tomtom or any other device needs to be charged - and i prefer built in satnav than cables hanging around from lighter socket.
Regards!
Peter