I know sooo little about BMW or any German engines, to be honest. I've seen some very good engineering in some, but as farcas designations and which are good and which aren't, I have no idea. About the only thing specifically I am knowledgeable about are the variations and history of Bosch Jetronic fuel injection.
You know what they say about women, if they spitters are qutters. It's the same here, when the S65 starts spitting them pistons like it's not tomorrow, you know that motor's a quitter. The V12 series is still good... Man how I want a 760Li. youtube.com/watch?v=KuK8gmBynhk
Brand new about 160k, used about 60k, and totaled (engine intact) about 25k. You'd be basically brain dead to get anything new form BMW, literally worst investment ever. It's just a 6.6 liter V12 twin-turbo. 600bhp and 800nm.