Forget the M135i if you want a weekend toy, the reason I love my old 335i was because it was easy to use day to day, and still could deliver 90-95% of what my old DC Integra R could do on an empty B road.....If it's a weekend your after, you want something much more special.
Also forget the new M3, its uses the same engine as my old E90 335i, and that came out in 2006!!!
If you want a weekend you, and BMW in-line 6's do if for you, you cannot beat the CSL, and it's an appreciating asset :)