I am reading and painting a picture of your car. We all love our cars and love spending lot of money to make them perform and look good. I would culculate the price of parts and labour, the second car that you are thinking of getting for parts and the price that you would get for your car. I'll bet you come to a price that would get you a nice 540i with lot of the things already done that you are planing. I have a e39 and know how much they cost to repair when things start to fall apart.