First decide on the time that you are planning to own this car and the purpose of this car to you.
If you are planning to sell it shortly, then add most favorite options that many would like to see in the car, like xenons, pana moon roof, leather seats, heated seats, heated steering, navigation, parking sensor with camera.
If you are planning to own it for a quite a good amount of time say like 8 years or so, then it does not matter what you add now, since the technology will be so different in 8 years. So add only what you need now and skip all the remaining so that you can save some money in your pocket.
Also the purpose, if its for you and you only, then think if you love music, if yes then add premium sound, if this is a family car with kids around most of the time, then you will be playing rhymes and stuff like that for which the standard sound will be enough. Like wise see if this car is for your wife and you, also see how many times you are going to be driving this, if she is going to drive more then check if she likes turbo or not, if not you can go for 28i, instead of 35i but you should looking to add convenience features like comfort access, power tailgate etc...which most women would love to have.
So determine what is the need and ask yourselves more questions and that will give you the best answer. Have Fun
