when using IR's you can turn off the post eq and see what it sounds like. i eq to work with the existing cabinets. adding an external cabinet changes the sound for the most part.

the pre-eq is for tightening up the tone most of the time. sometimes i use it to emulate the distortion response of amps that are not stock on the eleven rack.

there is no right and wrong. turn eq's off/on and find a tone that inspires you to play.