The Velineon system is 169$$
here at towerhobbies. Way cheaper then a Mamba Max system and twice the Amp rating. Runs both sensored and sensorless motors. Seems promising and will be even cheaper with the discounts from towerhobbies.
6 KiloWatt A123 Racer
GTP-Pletty Big Maxximum+RX8. GTP-C50-6L Hacker+RX8. CRT.5-Pro4+ZTW esc.
24s2p EVG SX 49.6mph Ebike.
18s4p Raptor 60mph Ebike. 11.5KW