My current set up in the FX as follows:
Park 400 920kv out runner, 10x4.7 or 11x3.8 slowfly APC prop, E-Flite 20A esc Kokam 1250mah 3 cell lipo, E-flite S75 servos and JR 610 rx.

920kv Park 400 out runner with 10x4.7 apc works very well. I have flown mine with the 370 inrunner on the stock box with the 12x6 and it also good. had the 400 740kv out runner but wasnt so good. Leblanc the 740 kv works best with an 11x7 apc slow fly, I think the 12x6 will load it a bit too much for a 10A ESC. My set up with the 920kv park 400 out runner and a 1250mah Kokam 3 cell produces around 150 watts, which relates to about 13 amps on a full charged lipo.
Got the 740 kv out runner in a green models spirit 3d at the moment and the 11x7 works good with that motor.