SM12, please update your profile with your location so that folks are aware. Depending upon which country you're in, it impacts which options/features are available to you.
Assuming you're in the US ... if you do not choose the Nav option, you will not get the AMI (
Audi Music Interface) which allows you to hookup an iPod, mp3 player, or USB flash drive in the glove compartment. In the US, the AMI feature is included as part of the Nav option and cannot be ordered as a stand alone feature. Just thought I would mention this in case you were planning to use an iPod. You'll still have the ability to use an
SD card for music storage, though, if you don't have the AMI feature.
BTW, regarding Macwm's comments about the summer performance tires, I have them on my A5 (since I opted for the 19" wheels) and find that they are quite comfortable and
surprisingly quiet. (What one considers to be "quiet" is subjective of course.) Macwm made some valid points. However, the suspension design on the A5/S5 yields an ideal blend of comfort and handling and shouldn't be compared to older Audi models IMO, because it's like comparing apples to oranges. If you haven't already, you should definitely drive a demo (if available) before making your final decision.