what is the difference between Mercedes E-class models?

i have decided to buy a mercedes car E-class model between 1997 till 2001, actually, there are so many models, (E200, E220, E240, E270, E280, E320, E420), … and i don’t know what is the difference between all these models rather than the engine size,,, is there any difference in options or in technology ..? somebody told me that the E280 takes 12 spark plugs, while the E320 which is bigger takes only 6 spark plugs,,, is that true..? and if it is true,,, which is better and more fuel economy…?

any body please explain …

if any body has any data on any model,, please tell me,, and i will collect the data …

also for options,, what is the difference between the "Avantgrade" and the "Elegance" and the "Classic" …?

Thanx for all ….

Why does mercedes make so many models…? so many confusion …!!!