How to determine amp rating ?

[suicideneil]

Watts / volts = amps
volts x amps = watts

That is correct yeah. I would pay no attention to the listed ratings of the traxxas escs as those figures at total fantasy pretty much; most likely calculated by adding together the rating of each FET used, rather than using the rating of a single FET as the rating for the whoel esc ( A FET being the chip that controls current flow essentially ).

It would probably be easier to just see a link / brand & model# for the motors your buddy is looking at, would be alot easier to give a thumbs up or thumbs down without having to know any of the actual ratings as such as brand, dimensions & kv rating are more useful to know generally speaking to determine what setup it could be used in & with what esc & voltage etc.