[jtkung]

In guitar modeling, it is apparent that the 2 most important aspects to the tone are:

1. Amp modeling, either using [A] component modeling coupled with circuit schematic and doing the circuit simulation (Fractal) or [2] distortion generator based on empirically derived parameters (Kemper)
   
2. Impulse responses (IRs) of the guitar speaker cabinet
   

#1 gives the amp's characteristic while #2 is like a sophisticated EQ of sorts.  IRs can be found from a number of 3rd party providers, allowing users to mix and match amps with a variety of guitar speakers and cabinets.