Need help with spur/pinion decision

hi guys, i hope you can help me out with this. I'm converting my Ofna Ravager/9.5 to brushless electric. i already bought a Quark Monster 125B and a Feigao 8xl. i'm planning on running 4s lipo. the thing i cant figure out is gearing. the 1/8th buggy has a center diff with steel spur/main gear. i'm planning on getting a couple pinion gear, 12t-16t. what should i do about the spur??? i've heard people suggesting replacing it with a weaker one just to have a wekness in the drivetrain. should i do this or can i still just run the all steel drivetrain?

oh yeah i'm also thinking about upgrading to the Torsen diffs.

any help would be greatly appreciated.