I put a set of the M3 Eibach springs on the rear of my car, which has a nice fresh set of Bilstein shocks on it. It rides really nicely, and with the Xi 15mm pads, you'd definitely be at the height you want.
That said... I'm a big fan of the flat ride principle of having a very wide gap between front and rear spring rates, and my thinking is that ultimately I'd want to pick up a set of coilover rears with the spring height adjuster, and then go with a very high spring rate TCK rear coil. I think that plus a standard shock/spring combo like Koni/H&R (or Eibach or whoever) up front could be the optimal setup for these cars. And I may well yank out my convertible's rear Ohlin springs and adjusters (the spring rate on those is 628 and they're progressive) just to do some experimentation.
Perhaps you think multi-million dollar ad campaigns make a beer taste better. Perhaps you're mouthing your words as you read this.