How do I connect my iMac to stereo equipment so that the sound completely bypasses my computer's own amplifier?
You need a 3.5mini jack to phono cable to go from the line out on your mac to the line in on your stereo. Only thing is you will still have volume control from your mac, not sure if you can it any other way.
I tried that. You still have to use the Mac's volume controls because the sound is still travelling through the Mac's amplifier. Connecting the Mac to a headphone amplifier that way doesn't sound any better than plugging the headphones into the Mac's headphone jack.
Well, your other option would be to use a decent external (USB or Firewire) audio device. No idea what works with Mac.