With the new MB V6, break in really is a thing of the past. These engines have an alloy cylinder with low tension piston rings.
I will not argue about your AMSOIL being superior to Mobil One, because I don't know. I will say that if it is indeed superior, it must be an AMAZING product. The Mobil One is an excellent product and way more than adequate for these or most any other engine. Given that oil and filters are already paid for by your purchase price, and given that the Mobil One that they now supply at no additional cost to you is more than adequate, I would wait for the warranty period to expire before changing to your favorite oil.
I personally have been changing oil and filter myself roughly half way between the MB paid for service intervals. I also put in a magnetic drain plug. When I do these home oil changes, I use Mobil One and a factory filter, drain it hot and let it drain overnight.
I hope you enjoy your C240 as much as I am enjoying mine.
Have a great day,