1st, how can you have a xl-5 rusty with a 12t motor? did you use a different esc? cause the xl5 esc can only handle down to 15turns.

2nd, the sidwinder with 3s would be very fast. but really, all the RTR brushless motors will blow your mind on 3s. even the hottest brushed motors dont compare.
you can multiply the #KV by the # of volts.....5700kv X 11.1=63270. so, with no load on the motor it will spin at 63270 RPMs.