Check out page 3 of this Tekno Instruction Guide. It provides a pretty good recommendations for kv vs lipo cells.
http://www.teknorc.com/images/V4_instructions_losi.pdf
I think it all boils down to efficiency and heat containment when it comes to motor selections. I've seen some guys run 6S and 1700kv motors and they are super fast and have no heat issues. There's ton of advice here. Good Luck!!