SanJMan-
For rideability I would stick with the 15" wheels. Tires and wheel cost adds up real quick! Low profile tires cost a lot more money than your normal Touring tire and they last a fraction of the amount of time. You are more susceptible to wheel damage with low profiles, as well as a rougher ride. but at the same time you are 17 and ride quality isn't typically high on the list of younger kids. TDi's are meant for long term ownership, ie 200-300+ miles. Once you break it in and it gets nice and comfortable, who really wants to give it up. Oh, and when does running all over 4 cyl gassers and give 6 cyl gassers and hard time in a diesel ever get old or uncool?
I understand that you are young, but TDi's are just always going to be cool in my book. The wife and I would really like to get a 2.5L Passat Wagon imported, but we are not sure if that can be done.
Just enjoy the car. Drive the snot out of it, try not to break it and if it turns out you don't like it give it back after 4 yrs and get something new. But hey, if it really grows on you and you decide you can't part with what I assume is your first car, you then have free reign of doing what ever your pocket book wills.
You can never replace the FIRST car! I know I haven't been able to.