The C6 is 4 grams lighter than the WS7III(big deal). You don't need a moded motor, so save your money. The RB's will out last those other motors & if you need more power than a C6 then I don't know what to say because it has plenty of power for any track any where. I'm running the C6 in an 8 with all silver springs & the power is very managable.