For what it's worth, I've used both "Itunes" and "Play" software on a Mac. I couldn't detect a difference. I use both toslink and usb connnections. I also cannot tell a difference switching between the two. I use Wireworld Ultraviolet High Performance USB Cable ($56 with shipping) and a Van Den Hul Optocoupler mk. II toslink cable ($119 with shipping)connected to an Airport Express.
