Mikel,
You would need two ESC's and a gyro to replace the Piccoboard. To use separate ESC's, you must have a transmitter with revolution mixing, or else use a heading hold gyro. If you already have or are buying a heli transmitter, then two GWS ESC's and a GWS rate gyro are about the same price or a little cheaper than the Piccoboard. If you get a heading hold gyro instead, it will cost about the same as the Piccoboard with HH module, and you will be able to use a 4 channel airplane transmitter.

The advantage to going separates, is that you can replace one piece at a time if it breaks or if you want to upgrade or go brushless. The disadvantage of separates, is that they can be harder to set up initially, especially if you don't get a heading hold gyro.

As for the BEC, you do need one, but it is built into most ESC's and also the Piccoboard. The motors need 8 or more volts to run, and most receivers, gyros and servos will burn out with more than 5.5 volts. The BEC takes the 8 or 12 or more volts from the motor battery, and drops it to a safe level for the receiver, gyro, and servos.

Jeff