new e70 x5 4.8i 2010

[adevster8]

so I just bought a new x5 and had a few questions since its my first BMW and German car as well.

1.) I was tempted to buy a performance drop in filter to get a little more air in my engine. For now i just got the Mahle filter since I've heard it filters better than K&M or Afe dry filters. Should I opt for a performance one instead or stick with the stock one?

2.) I live in Seattle where winters don't generally get under 20 degrees and bought castrol edge full synthetic 5w-30. Is this optimal?

3.) Do I need to buy a Mahle/Mann oil filter or will Wix suffice? All of my autobody stores only carry Wix it seems

4.) I put an aftermarket sound system in the trunk since I wanted a bit more bass. If its not tied into the factory system whatsoever, would I have anything to worry about voiding an extended 2 year warranty?

5.) Any other suggestions or easy ways to make SUV run smoother/perform better? I bought this v8 beast with 80K but it drives like a dream, I'm just paranoid things will go wrong so I'm wondering if there's any more upkeep I should perform as I just bought the car. I've always had Japanese cars which require 0 upkeep and run fine so now I'm prepared to be on point with maintenance.

Thanks!

Devin