Where you live plays a big part in which options you can get. U.S. customers can only get 4matic in the C300, so that limits your model choice right away. Same situation with the manual transmission, its only offered in C300 non 4matic cars, so your choices are limited once again. Another strange situation revolves around the 18" AMG wheel package, its only available on non 4matic Sport cars as a factory option. Once you decide on which model you want, next up are the options, P1 seems to be the most popular added option and its the only option I added to my car (except if you count metallic paint). Other popular options here include the ipod adapter, MM package and the pano roof. I myself had no need for those options so for me they didn't warrant the money spent on them, but I will say that the 12 speaker surround sound system is quite nice and that the panoroof looks great, even if its not really all that useful.