[Si Coe]

Was that you practising down at the track when I left? If so that car is crazy quick and probably too much!

Which motor to go to will depend on the exact Castle setup you have. If you've got a Sidewinder esc you are stuck running sensorless, whereas the Mamba Max Pro has the option of running sensored. Sensorless systems are most common for bashing about, but racers almost exclusively use the smoother more controlable sensored systems. If you have the Sidewinder I'd just sell the esc and motor together and go for a full sensored system. If you have the MMP you could just swap out the motor for a sensored one.
For reference motors that are quoted as 3800kV tend to be sensorless, motors quoted as 6.5t are sensored.

Speed Passion motors have a rep for being a little 'soft', lacking punch compared to similar winds from other brands. However that makes them smoother and easier to control so many people like them. They are also very cheap for decent motors. The main downside is the built in plug system which looks great but you will soon learn to hate....

6.5t is the most common wind for 4wd's these days, but Bury's track layout tends to be more technical than an outright power track and you can run lesser winds without being left too far behind. Your cells are OK, but have a relatively low current rating so I wouldn't use them with a monster power motor as they won't last long.