Volvo will be difficult to sell, unless you are planning on writing it off too, Maintenance will also be an issue, However i do understand that the heart wants what it wants.
The straight 6 in the BMW is very reliable and highly under stressed, actually its one of the greatest engines currently on the market. Parts and maintenance will not be an issue,(there is a whole community for this car) finding an indie for it also wont be a problem, The gearbox (8 speed ZF) is also the best gearbox currently on the market, Once you get bored with your 250kw you can mod it to 300kw easy.
All i am saying is the M140i = Perfection and it literally has no shortfalls. nada.