I have a stock emaxx and I want to upgrade to brushless motors. I want more speed and power. I was thinking about getting the mamba, novak, or the hpi motor. What kind of connections do they have? Can I use my 6 cells with black traxxas connections.

You will need to get new matching plugs unless you would happen to get the Traxxas system.

I'm really confused as to what brushless upgrade motor would be best. What do you suggest?
Thanks.

Mamba and Novak both make good systems. I would recommend one of those.

Mamba and Novak both make good systems. I would recommend one of those.
Yes but not the standard versions.

For the E-Maxx you either need the Castle Monster Maxx systems or the Novak HV-Maxx systems.

I put a Novak HV system (7.5 motor) in my Emaxx and it works great. the novak system comes with tamiya plugs on it , put it should be no issue to change the ends , Traxxas sells the plugs seperately. If you want the part numbers let me know.