Hmmm...I'm in Dallas and in the same boat. Well, car.
I guess there are two ways to fit a double-DIN in these cars: move the climate controls down, thus creating the double-DIN space above it; or changing the dash top as in the link.
The first method seems to work well and has been done a lot. I was about to go that way (until I found this thread), my only concern being whether the BMW's electronics would be compatible with aftermarket head units (satellite, Bluetooth, Nav, etc.).
I'll now investigate the up-top method shown in the link and decide which way to go. Sounds like Patryk (?) would know about the electronic compatibility issue.
Dallas, TX USA
Burnin' gas for 50 years and still going!