Amplifier for gwinstek SFG2004 ?

[zen18]

HI to all !
This is my first question to this forum and i really hope that someone can point me in right direction.

I would like to create circuit that i can use as amplifier ( or some other solution ? ) and hook that to input of SFG 2004 function generator. The goal is to test different metal plates ( aluminum , copper ) and check the effect that is caused by generated frequency.
Frequency range will be from 5HZ - 5KHZ and i was thinking to create some 100 - 150W amplifier.

Problems and wishes:
- how to apply this frequency to plate ( i think that speaker is the best solution, but i dont know if this would produce right effect ).
- would it be possible to hook up some "electrodes" directly to plate and "bomb" the plate ?
- if its not too much trouble to create, i would like to expand this frequency range to MHZ range. Question is, how much power would i need to make this work. BTW. planned carrier waves are sinusoidal and square waves.   
- at the time, i would like to start with lower frequency and power but in future, it would be nice to see how this would work in MHZ range ( at some resonance frequency ).

OK. Your ideas and comments are more then welcome !
Z.