I just got my 2018 E63S sedan this week. I resisted going for extended warranty at dealership as it didn't seam to be that great of a deal. I own the car outright and usually keep my cars 8+ years and drive less than 9,000 miles a year. I did get the optional 3D sound system and the premium package so I have lots of electronic components.

Dealership quoted me $6,300 for 7yr / 75k Mercedes Warranty
Also found another MB dealer that would do it for $5,900
and lastly got quoted on a third party Fidelity Platinum w/ $100 deductible 8 yr / 80K for only $2871.00
I am a little skeptical of the 3rd party as my online research shows a fair amount of unsatisfied customers

Last consideration is I'm planning to get a Eurocharged tune later this year. So any opinions on these warranty options and any thoughts on warranty coverage with tune? Thanks.

You can't count on your warrantee coverage if you get a tune, your car could be flagged. $5900 for the 7/75 actually sounds like a pretty fair deal. The warrantees have gone up quite a bit in the past few years. I think I paid $4200 for a 7/100 on my 2012 Amg wagon. Forget the aftermarket warrantee, from what I've seen those are generally not worth it.

If you have Schools First Federal Credit Union, their extended warranties are fantastic. I got a warranty for my '04 SL600 for 72/72K miles with a $250 deductible for $3,277. Full coverage. And I have definitely used it without any issues. Credit unions sometimes have really good warranty coverages. I'd look into it if you have a credit union you associate with.