I really don't know a lot about the electric ones, but I've seen a few on youtube I've been really impressed with... like this one that's got dual 4000 watt motors and de tuned down to 5600 total watts but it's insane with the 2WD... https://www.youtube.com/watch?v=xP6fAPJa7cE
I've seen a few with single motors between 8000 and 13000 watts that are really fast too... but we're talking big bucks for these or I'd have one... lol
My guess, and this is just a guess is that in order to have similar power as a stock China Girl 66cc you'd need about 1500 watts but electric motorstend to have full torque at just about any rpm so it may take off from a start a little better than a China Girl... The one in the video I posted is just awesome and I like that it can spin both wheels on take off like that... I may build one of those once I get my business going... just a little too rich for my blood right now because the money I got needs to go to shop rental right now.