I've a 911 and a diesel; use the diesel for long freeway trips and the 911 for fun. Let's face it; the diesels are not terribly exciting to drive (except maybe when trying to "accelerate" during a slide on a wet road). If you've not driven a true high performance car such as a 911 go find one to drive.
Keep the diesel, too; it REALLY feels slow after you get out of the 911. The 911 is a very reliable car with a vast store of knowledge behind it and a parts network just as extensive as mercedes. The performance upgrade market is MUCH more robust.