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Of these, which car has the best deal....? (BMW or Audi)?

I'm getting my first car next month (I'm 17) and my parents gave me a $20,000 limit. For a girl, I'm really into cars because of my brother but I would just like a second opinion. Please don't call me a brat, I come from a privileged family so a car like this is what my parents prefer and I am one to really keep up with what I own. Which ever car I get would be thoroughly taken care of. Also, keep in mind that all of these cars have no warranty (but they are available) and that they each have no damage or accident reports and have an overall pristine condition.
Of the following cars, which do you think is the best deal:

-2007 Audi A4 2.0T/ 64,276 Miles/ Automatic/ PREAMP AND SUBWOOFER/ $17,000/

-2003 BMW 7 Series 745Li Sedan/ 76,815 Miles/ Shiftable Automatic/ NAVIGATION GUIDANCE/ $19,000

-2002 BMW M3 Convertible/ 84,620 Miles/ Sequential Semi-Manual/ NAVIGATION GUIDANCE/ $19,000

I would pass on all 3 of those. Yeah they are great cars but come on do you really want a car with that many miles? You know stuff is going to be breaking pretty soon. Look for some USA made cars that are used but still pretty loaded you can find much better. Yeah it wont be an audi or a beemer but it will last longer. I remember seeing a dodge charger daytona (special paint, limited number produced, all the best electronics best stereo system,gps, leather) R/T (hemi engine 350 horses sure to give any one of those cars on your list a run for its money) it was a 2007 with only 3,000 miles they wanted $20,000. So basically you have a 4 door sports car very fast, looks great and still has a warrenty for the next 55,000 miles. It was an automatic with auto-stick (manually shift gears with out having to mess with a clutch) I would not just concentrate on high end luxury brands when you can find a lot better of a car with a lot less mileage.