My C7A2 (CA M15-based) with stock CA gears is running an MS110SP spring. Shoots a nice steady 385 fps. But with standard CA gears and the CA "high torque" (I use that name loosely) motor, there was considerable trigger lag, even while running a large 9.6V 3300 mAh battery. I think it'll be even worse if you're running high speed gears. It took a Systema Magnum motor to kick up the initial rof (19 BB/second) and decrease trigger lag to almost nothing. Even then, I'm thinking of throwing in a high torque gear set. I value a responsive trigger far more than high rof.
IMO, high speed gears should be saved for sub-350 fps setups. At the very least you'll want standard ratio gears with a setup that's in the 400 fps range, especially if you're running the stock CA motor.