The HPI Flux system is made buy Castle Creations its exactly the same as a Sidewinder system, I'm running the Sidewinder 5700kv in my Blitz and i can say its very good, heaps of power, i have tuned it down a bit and changed the gearing too 16/88 to get the temps spot-on...
I think youl find you can also find the Sidewinder System for a Cheaper price as well..