That Z4 is a beautiful machine. THe lines and proportions are near perfect.
I just noticed when I looked at the Z4 pic you posted that there is some definitite commonality between BMW cars and motorcycles.
Check out the gas tank on my R1200R.
Back to your original question: I like the wagons and I like diesels. My GTi had a bad electric system but I do like the new Jetta Wagon diesels.
For a more sporty option I would go with the Z4 or Audi A3.