Got my 9918 today..

[RC-Monster Mike]

Higher voltage will potentially provide more power to your truck, but not your servos. If you have decent steering servo, the controller bec will give you plenty of power. For Aluminum 40 series wheels, there aren't a lot of options. I don't stock any, but can get some from my distributor. The ones there are quite pricey, though($200+ per set)!