The 3 Series and te powertrains in them are very reliable. My car has over 203,000 miles on the odometer -- no rebuild, etc. I wouldn't worry about finding soemthing under 35k miles. You will only end up paying several thousand more $. I like the 50k mark myself, because most cars have just come off warranty or sometimes still have smoe left, which is good for most of any repairs that may become necessary while still recovering from the down payment (or haveing dished out cash for the whole thing).
When looking at cars' records, pay attention to see if the dealership (or whoever worked on the car) suggested any work that needed to be done. See if the owner actually had teh work done later.You don't want a car that has been neglected.
VW's aren't what they used to be, by the way. They are harder to work on than are BMWs, which will make your life harder if you work on your car yourself, or will make a bigger dent in your wallet if you have to pay for all that labor time. VW's also don't handle anywhere nearly as well as BMWs, which may or may not matter to you as much.
Acura's are excellent cars. If I were restricted to the three makes you mentioned in your original post, Acura would be my choice behind BMW. They handle a lot better than the VW, have nice amenities and will be very reliable.
It;s your money and it will be your car. I suggest that you test drive the cars you like and take your driving experience into consideration.
Welcome to UB.c and we hope the car that is right for you (which hopefully will be a bmw