You could PM Chard as he's had numerous BMW's and I've PM'ed him about them. My choice would be a 2003 540- the last year of that style and the fastest. I almost bought one before I bought my Boxster. It was a mint, low mile car and I walked away after reading an article stating that the engines are complex and difficult to work on ( for a back yard mechanic). That didn't stop me with my Boxster though!
I still long for that cool silver sleeper- so solid and fast!