Questons on the SEL's

[Hatterasguy]

Hi this summer I will be purchesing my first MB. I definintly want a W126 car with a long wheel base. What are the main diffrences between the 420, 500 and 560SELs. I would also like to hear from some owners, how do they preform and how difficult is the maintance? What types of problems should I look for with these cars? I know the timeing chains should be replaced at 100K miles. Also how long do these engines generally run before needing major internal work? Hypotheticly (sp?) if I by a 560SEL with 160k on it could I get another 100k out of it without a rebuild? I ask this because I am looking for a car to keep a long time, I only drive 9k a year so it would take many years for me to put 100k on it.
Secondly I want a car with guts! My current car is a Camry with a 2.2 liter 4 banger. It is so slow. I am looking for something that will push me back in my seat and does not run out of steam at 90. That is why I am leaning towards the 560. But how are the 420s and 500s performance wise?
Also last but most important, what can I get for 5-6K. I have been watching e bay and have seen very nice looking 420SELs with around 120-140k on then go for 4-5k. What can I expect to get from a 500 or 560 for that kind of money? I will do all of the work needed myself.
Thank you in advance for the help.