what's the amp loading on each of those motors with the props you are running?

80% times 1500mAh = 1.2Ah times that by (the 80% is to account for the MFG's liberal ratings on lipo discharge rates, and also reduce the heat from the battery during discharge, lower rate = same amount of energy dissipated over a longer period of time which means lower battery temps)

15C = 18A total max for EACH motor
10C = 12A
20C = 24A

hopefully that makes sense. Also depending on how you want to do it, I dunno if you are running the BEC from the motor ESC, but alot of people recommend that you only hook one of them up to the receiver, that would make it a bit more complicated with your setup, but it might also be something you want to look into.

GL =)