Drool. The 540i 6-speed is one of the cars that originally drew me to BMW. Kinda like a ti, if I ever got one, I don't think I could ever part with it. As mentioned, look in the For Sale section here. You're likely to find a car that's been looked after and better maintained, and with fewer questions about it's condition than one you'll find on Craigslist, Autotrader, etc. Good luck with the search and welcome to the Org.
Justin