If you are getting the pro-car version it is cheaper here
http://www.b-p-p.com/products.php?cat=36
He also has a lot of combos for good prices. I am running a Mamba 6800 motor and Mamba 25 esc on 2s in my 18T and it is plenty fast for me. You might want to think about the Wraith 7K it has a 25mm dia. can where as the Mamba and C4 are 20mm dia cans and I think the Wraith is a little longer also.