I actually got pretty cool tones on one recording by tracking direct into software (not even an amp model - a distortion modeler and a modulator), and blasting

I actually got pretty cool tones on one recording by tracking direct into software (not even an amp model - a distortion modeler and a modulator), and blasting the monitors loud enough to get feedback. You're absolutely right about the importance of a little feedback on the tone (even if feedback isn't the goal), but there's more than one way to get it. Frank Zappa used to record with little Pignose practice amps in an echo chamber, and got his feedback off the studio monitors as well.