An introduction to computer audio
You can add all kind of plug-ins
Isone Pro binaural room simulator
This plug-in is for headphone listening.
It is not only a cross feed but also simulates room acoustics and allows you to choose various types of speakers.
My experience is that the soundstage over the headphone can be made almost identical to listening to a pair of speakers. That horrible STEREO image, inherent to headphone listening is gone.
No need for QuickTime anymore.