I can only comment on the cars themselves...not really ownership of them.
Now personally...I'd go with the Jaguar XJR just because I love them. The only holdback would be the fact that it's automatic only but I know Jaguar's clientele wouldn't want to be bothered by a third pedal anyway. I like how they look, I think they have a very warm and coddling interior, and you don't see them as much as you might any other car on that list. Maintenance is a huge issue with those cars though, plus that "Leaper" hood ornament is pretty easy to nick.
The best of the lot has to be the M5 though. If you want brute-force power, then get a Merc, but I think the BMW blends the best qualities of every car on that list.
I think the Lexus would be too boring, and do you really want to proliferate certain stereotypes any further?
What do you want though? If you just want plain old luxury, go with the S Class or the 7 series...the 7 leans a little more towards the driver's car side and the S Class more towards the luxury end of big cars. Again though, I really feel the M5 would be an excellent blend of all the high-points of the cars you've listed. Sure you may not get the gadgets of the Lexus or the old-world luxury of the Jaguar...but it's got loads of power, it's agile in the curves, and it looks mean as hell.
Good luck man.
