I think you can use the Jazz 40 with the Hacker Motor on 6s Lipo without problems. If the Jazz controllers are properly cooled, they can take much more amps than Kontronik says. Here in Germany, some Helicopter guys are getting up to 2,9kw out of their Jazz 55-10-32 on 10s Lipo, thats 85amps
So if you put a fan or a small heatsink on it, your Jazz will take up to 1100watts on 6s Lipo without thermal problems, i don't think that the motor needs more in a such light car.