What is the best setup 8xl and warrior 9920

[sluggie24]

Hey guys. I just ordered a 8xl motor and warrior 9920 for my E-Maxx. I'm planning on running 20/66 gears at first and might adjust from there. I have 2 7 cell 4200mah batteries for it already. The write up on the controller says it will handle 20 cells so I'm tempted to add another 6 cell pack on. I'm just looking for a sick truck that can wheelie all the way down the street and has a great top end too. My question is will this set up handle 20 cells or should I stick with 14? And does anyone know what kind of performance I might be looking at with either set up? The rear end will keep the stock ratio for now since I just got finished building up both diffs.