I have an amplifier that can be driven by a USB connection from my MBP, but I would still like to have sound sent to my speaker-out jack on the computer itself. When I use the external amp with the USB, I have to change the sound drivers on my computer, and the speaker-out jack is silenced. I know this is a long shot, but is there any program/technique/setting that will enable both devices to play the same audio simultaneously? I need to use both sound systems at once (I'm running sound for a small event and need to set it up like this: MBP > USB > amplifier > stereo speakers (which lack a subwoofer); and MBP > stereo out > computer speakers w/subwoofer. both speaker sets playing the same audio source. is there a soundcard emulation program that will enable both outs to be used? And no, I can't just add the subwoofer to the signal chain with the amplifier: it's got different connections and needs to be amplified with subwoofer frequencies.