Hey all, I'm a newbie to the forum as well and contemplating putting in an order for the 328i as well.
I'm going for the sunroof as well... in my current car it's open only 20% of the time, but I love it for the extra light it brings into the cabin.
From all of the reviews on the 328i it sounds like the Adaptive Suspension is a must. Most reviewers have panned the standard suspension (Car Magazine, Wheels) & are praising the car with the adaptive setup, so looks like I will tick that box as well. (having said that, I don't think anyone has reviewed the standard M Sport suspension).
Because I'm ticking the adaptive suspension box, I'm going to do without the HUD (as cool as it sounds). I was also thinking about the Professional nav as well, but to me the suspension was more important. The 6 inch screen on my current car is plenty of visual real estate.
Long term, the 2nd hand buyers won't appreciate the additional $$$ you sunk into the other options. The comfort access & BT/voice recognition sound nice, but don't seem essential.
Even though I'm not considering it atm, the +DAB seems like it's worth it & you will enjoy AM more. I listen to AM about 40% of the time and can appreciate the difference it would make. I'm thinking of the heating all seats instead (though this thread has got me thinking).
The brakes sounds like you are thinking of taking the car onto a track, so you probably should to minimise brake fade.