The list at the moment is looking a bit like:
Z4M Coupe
E60 M5
E92 M3
E92 335i or d
Audi S5 (V8)
C63 AMG
Jaguar XK
Lotus Exige S
Porsche Cayman S
I really don't know about the above yet, I need to book some test drives and look at a proper budget. However with fuel prices dropping it is possibly a good time to get something with a bit of grunt.
Cool list but... What's the 335d doing in there? Seriously, you can safely write that one off and keep only the 335i in your list
I'm not saying the 335d is not a good car but diesel engines are simply not my thing: I don't like the vibrations / feeling diesel engines give to the cars they're in. My father-in-law just bought a new Mercedes and I had no idea it had a diesel engine: he gave me the keys and said "try it"... I turned it on and said, surprised, "Oh, it's a diesel" (well, in french) and he could see I was disappointed. Some people don't mind diesel engine but seen your list, I'm pretty sure you'll enjoy the other cars more...
The E60 M5 seems like an insanely cool car. I've been thinking about the E63/E64 (?) M6 with that same 5.0l V10 atmo engine but then in my country yearly taxes on such engines are really wayyyy too crazy (something like 5 K EUR
every year just to keep your license plate, then you need to pay insurance, etc.). So as soon as they're a few years old, these cars' value do really fall like mad around here: you have car that were, what, 100K brand new which can be had after a few years for 25K... Because nobody wants them: there are not many people willing to put 25 or 30 K in a car and then have to pay 5K every single year for the "road tax" / "license plate". Not too mention that the first time it becomes yours, that's another, one-time, 5 K gift to the state (I think it's even more than that: something like 8K: it's dependent on the size of the engine, not its power, so big fat atmo engines are very badly penalized).
So I could buy, say, a 2006 M6 for 30 K but the first year it would cost me, without any insurance, 40 K or even more. That's 10 K lost immediately. Not too mention insurance costs etc.
If in your country (U.S. ?) you don't have these crazy yearly road taxes for big engines, then a M5 or a M6 with that 5.0l V10 engine seems like something really sweet.
You should maybe add the M6 too: I find it even better looking than the M5 and even less common (I'm not saying that a M5 is common)
I don't know neither Audi nor Jaguar XK very well but I like your list