Can't help you much on price either, but I think 2006 was a good year. A nice, sporty feel from the engine and most of the car and drivetrain is based on the E46 3er so that makes it slightly easier to work on. I've ridden in an M sport model and it rides fine for my tastes but I guess roads in certain parts of the US are pretty bad so take it for a thorough test drive, of course.

The 2007 builds tended to have some issues with the 6-speed automatic transmission that are more pronounced in urban driving. The drivetrain itself is softer and more efficient and there were some interior improvements but given the rarity of 6MT 2007 models, I'd play it safe and go for the 2006 if it's got a clean history.