Like this? http://projectguitar.ibforums.com/index.php?showtopic=15379
Actually, that's about what I was trying to get at, at least the part about conservation of energy. There is not actually a signal boost in that 100hz band, but it feels like there is one. In your model, the 100hz waves are being reinforced by the "tuning" of the wood structure, keeping that frequency going in the string's vibration. Similarly, when you listen to the unamplified guitar, it sounds much louder than just a string vibrating, because the string is driving the wood. Air is the poorest conductor of sound. If you took the cone out of a speaker, it would not sound too good either. The cone is there to push air. When you place the butt of your electric guitar, or tuning fork on the table top, you are giving it a larger area to transfer it's energy into sound waves. The energy was all there when you plucked the string or hit the fork, but now more of it is being converted into an audible form.
Any time we select a certain material, use it in a certain way, add a piece of hardware, etc., we are affecting the way the energy from the string reaches our ear. In an acoustic instrument, this is a relatively direct relationship. In an electric, it is a bit different- you have to realise that the way the string drives the wood doesn't necessarily affect the tone you hear from your amp. But the wood IS being set into motion, and that in turn does affect the way the string vibrates.
FWIW, the term "tonewood" almost always makes me cringe. I feel it is valid in some cases, such as "mahogany is a warm tonewood", etc., but to say that one wood is a tonewood and another is not, is really misleading. I don't know where the term originated, but it has come to be used in a rather snobby way, as if some luthier/deity has certified this particular chunk of wood as "tonewood" and anything less is stovewood.