Newbie needs help with brushless e revo setup

[hk3948]

hey guys. my first post on this forum. im looking to get a brushless setup for my e revo. problem im having is deciding on which motor/esc combo would suit me best and thought i would probe your expertise for some advice.

basically, i already have a pair of 2s 4900mah 25c lipos so will initially be sticking with 4s. to be honest, i dont really see a need to ever go 6s if i am happy with the performance i get from 4s.
i am after a big increase in torque and top speed from whatever setup i get. i dont race and will be using just for bashing

so far, im leaning towards getting one of the neu motors with a mamba monster esc. have a few questions?

1. cant decide whether to go with a 1512 or 1515. not sure on why id pick one over the other

2. what are the advantages of 6s over 4s. surely with the right motor choice and gearing i could achieve similar speeds to those with a 6s. is it worth the extra breakages etc associated with the power of 6s.

3. im not sure of which 1512/1515 would be the best choice. any thoughts and why.

4. any suggestions on the setup youd recommend

i really appreciate your time and help everyone.
thanks