power amplifier help needed

[hydro]

hi guys
i need some info on a problem i have.

i have a signal generator creating a 40-50khz square wave with 50% duty cycle.
this output is very small, and low powered.

i am looking for a power amplifier that can amplify this frequency to about 100watts but i must be able to vary the power given like on a stereo amplifier.

i would also like the output of the amplifier to be 50ohm so as that i might put it through a band pass filter and then into a dipole antenna

any help you can give me would be great.
1 thing i did think of was using a stereo amplifier from a car, i have found one that has frequency responce of 20hz to 50khz, would an amplifier such as this allow my frequency to pass through as a square wave???? also an amp has 4 or 8ohm output is there a way to take this upto 50ohm output???? i have read about baluns and maching transformers but havnt a clue where to begin.

please help

[5B4AJB]

Yes, an audio amp will do this, not very efficiently, but a few hams use this method for the VLF bands.