One problem with using an RP2000 and an external amp, are the AMP models and Cabinet emulation settings in the RP2000. If these are on, you may have undesirable results when listening through a guitar amp or pre-amp etc. You can turn the models off and still use the digital effects. This is best used with an effects loop of the amp in question. If you want to hear the RP2000 at it's best, you may want to listen to it through headphones or turn off the models.