Why 100 Watt Head
I am curious. Why did you want a 100 watt amp in the first place. Was it becuase you thought that the sound you want can only be gotten by using such an amp. I think you should take the advice of the majority opinion here and scrap that 100 watt amp idea. Get a pre-amp. But, before you do, pick up a book on recording, home recording or whatever, a basic guide if you will. In any number of these type of books, you will find an explanation of what a pre-amp does and how to use it. This will certainly give you the information you need.
Hopefully, someday, you will be able to hear the difference and hear what you are doing and questions such as the one you asked will be moot.