They say if you upgrade to the 8 cell battery packs (because they are 9.6 volt and not the standard 7.2volt) you need to use the kyosho Battery Protection Unit #16199 BUT... most people run their cars perfectly fine without it.
Personally I wouldn't worry about it. You said in your first post you want to hop it up and make it go fast so you probably won't be keeping the standard ESC\Receiver unit?