Ive had a 745,M3 4dr,M5, and a 540I. Out of all of them the 5 series is by far the most well rounded and overall excellent car. Its personal preference on generation but for the money it is really hard to beat the value that you get in an E39 540. You can get one in the last year of the E39 which im thinking was 2003ish very cheap for what you get. The e60 lost alot of the true driver feeling and in my opinion gained alot of ugliness. Wheels and a simple axle back exhaust are all that the E39 540 needs to be an incredible driver car. Make sure that you get one with the sport package or youll hate the drive of the car. Sport package E39 540's are denoted easily by the window trim. If the window trim around the door windows is black then you have the sport package in front of you. The sport package in those cars gives you better rear end gearing, about an inch or two lower suspension, larger sway bars, both front and rear, higher end leather, and more adjustments on the power seats. Overall go drive whatever youre considering before you do anything.