At the end of the day if you ask the LOC brethren whether you should swap the bimma for the Lexus then they'll say yes. Much the same as if you asked the Audi forum whether you should shop it for an A8, they'll also say yes!
I think you need to go and have some test drives (as hard as that appears ) and choose which car best fits your needs be it comfort, sporting pretentions, space etc and then the other factors such as economy. Once you have decided the car you'll then need to spend time on the appropriate forum looking for information, pitfalls, servicing/maintenance info and maybe even a club members car which'll more likely than not have been looked after.
I suppose if you're already on here looking for info I reckon your mind is made up :D , start trawling the adds or ask on here if anyone has a decent one for sale :winky: You'll be grinning from ear to ear in no time.