The thing is, The servos which are already installed in your Stryker B are (I think) 5 wire servos. Standard servos are three wire. All standard Receivers use Three wire servos (as far as I know anyways). so this is why you would need new servos.

The whole reason for this goes back to your motor.

As the motor is the first thing people tend to think about when they are hopping up any airplane (my opin).

The idea is that you use a brushless motor. The motor you are going to need uses three wires for its magnetic coils.

The only thing which will run such a motor is an ESC and there in lies the begining of your problems.

To use an esc you need a radio receiver which will allow you to plug one in.
The ones which do this are Standard Receiver boxes. Case in point, the one included with your plane is proprietary (they are made specific for parkzone and their applications and hence are for the most part, incompatible with Standard RC equippment)

so then...

you buy the motor, the propeller, propeller adapter, the esc and a new radio receiver box... NOW you also need a standard transmitter and propper crystal pairs on the same frequency before you can use such a Receiver... not to mention that the standard radio receiver will now only be able to use standard Servos.

so... in a nutshell.
YES you need to buy new servos....

Again ill suggest that you just buy the Ready to fly (RTF) stryker C.
Soon thats where my money will be going...
either that or i get the ARF version and just use my standard equippment on it since I already have those lieing round


good luck

xero.