I have to make up more rules otherwise I can't pick: you said 'drive' not 'own', so I'm imagining I'd get the car for a week or two and do whatever I want with it.
Sorry, I tend to take these sort of fantasy questions too seriously.
-Continental GT: Too soft. If I was going to own one of these, it'd be higher ranked, but to enjoy for a limited time I'd want something sportier.
-CL-Class: That's sort of open, Benzes have such a wide range on many models. What's the entry CL, a 350? If it's a 55, I'd rather have the Continental. If it's a 65, I'd still rather have the Aston.
-6 Series: I like the 6-series very much, but it takes an M6 to equal the performance of the DB9 and reviews say it's suspention is extremely hardcore.
-Jaguar XK: Am I the only one who likes the last generation better? Mechanically, they're almost the same, and I think the new one looks much worse.
-DB9: I'm suprised to find it weighs (in manual form) exactly as much as the M6. The suspention is supposed to be quite hard for a GT car, but not as much so as the M6s. Given that, I suppose it wouldn't do quite as well on a road course, but I'd still choose it over the M6. Barely, though.
-Maserati GranTurismo: I have some irrational bias against Maseratis. It seems the only ones I like are the 70s and 80s cars that real Maserati lovers hate. Besides, the GranTurismo is pretty slow and weak compared to the compitition here.
That's the car to play with for a week though, if I had to pick one to live with, it'd be the CL (as long as it's at least a 55).