You can spend more, but you can't buy a better oil than Mobil 1 0W40 for your Mercedes.
Believe me, if it makes you feel better to spend more, you'll pay outrageous prices for lots of things on that car...
And I would just use the MB Fleece filter. It's relatively inexpensive, even at the dealer.
I'll have another Mobil 1 0W40 UOA soon, as the S600 is due for its B service next month, but here's an example of how well that "cheap" oil held up in the M275 V-12 twin turbo: http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3383451/Mobil_1_0W40,_9,186_miles,_200#Post3383451