I'm a little surprised that you suggested the 335i as an option after saying you wanted a low maintenance reliable car. Maintaining a turbocharged BMW with high miles may be more involvement than you want. If you really want to go BMW, perhaps find a 328i, as the regular straight six (non turbo) is actually fairly reliable, although maintenance can still be very pricy, especially if you go through a dealership.
If you really must have a luxury nameplate, I would suggest getting something used from Acura, Lexus or Infiniti. An Acura TSX would be a great choice, as they are known to be fairly bulletproof and you might be able to find one with well under 100,000 miles in your price range and they should be good for 200,000 with proper maintenance. IS250 that you suggested is also a great choice, and they are rear wheel drive, unlike the Acura.
If you remember one thing, it is that you must be cautious when buying high mile luxury cars, as many of the higher end models with lots of gadgets have more that can go wrong. The Acura is a good bet because they were relatively simple.