My vote would be the X1 xDrive35i. Best compromise between all major factors. Small like the M235i, got the N55 engine, AWD, spacious and more practical.
X5M would also be a good option but original S63s are horrible motors for what they are. Definetly better than the N63 of the time, but not by much. Only get a X5M E70 if you are willing to deal with the major issues these engines have, including rod bearings.
E90 320is never came with a straight six. At best, these came with some form of NA 4 Cylinder. All other models after the 320i came with some form of 6 cylinder. 320ds also come with 4 cylinders, though these were turbocharged. Unless it was engine swapped, I would be very skeptical.
Seller doesn’t state how many KMs the car has done, so that is also a red flag, unless it’s shown in the pictures.
I would stay away from this one unless you are looking for a project car, and are willing to gamble the whole way.
Always