Unless the European models are radically different you won't be able to use the Alpine because it will require you to replace the head unit which controls most things electronic in the car. If you use a phone, it will not be integrated unless the new head unit provides such features, you will not be able to use the voice activation unit that you've seen much discussion on this board around.
Certainly, the steering wheel controls will be extremely difficult to integrate into a new head unit and I've heard, but not verified that many other electronic pleasentries are rendered inoperable when the head unit is replaced, i.e., all computer associated features.
We are all there with you in wanting to spend the money and the time to replace the entire sound system, including NAV but live in fear of loosing much more than we would gain.