brushless conversion questions

[rcsammy]

hmm well if i go for an X1CR or a hyper 7 i already own nitro versions of them so i have a few spares, although the hyper 7 is a bit old for racing

i tried the calculation for continuous rating (mah capacity x C rating = continuous rating) i picked one at random its 4s 6000mah 20c(what does the C stand for?) so i get 120,000 does that mean 120A continuous?
then there is a 5000mah 25C version which works out at 125A continuous

one other thing is a charger, do i need a seperate balancer(right word?) and charger or do they come in one
does anyone have any recommendations?