For the version 3.0 of the copter, I am planning on getting 3 sets of the HK-T250 CCPM Electric Helicopter Kit which are only $30 each.

I will need 9 servos (3 servos per rotor swash plate) , and these look great value at $9 per pack and had great reviews. Turnigy 1800A SERVO 8G/1.7KG/.10SEC (3-PACK)

The microcontroller will have to control the speed of 3 motors, as well as 9 servos. Initial thoughts on this seem to tell me I may need 1 processor per rotor (controlling one rotor motor and 3 servos).

So 3 processors (one per corner) and then a 4th processor collecting data from IMU, and giving instructions to the other 3 controllers.

Or maybe use an ATmega1280 (Arduino Mega) which has 54 I/O channels, 14 of which can drive PWM. I would only ned 12 PWM channels.