I'm discounting you using something super el-cheapo here, since in that case you probably can't tell the difference anyway. There are a few main scenarios here that depend on what you're listening with (and of course your ears, but only you can make the call there).
I have that machine (MacPro3,1), and have used an external USB DAC with it. I was wondering whether the sound quality output from an external DAC would be significantly better than the output from the internal Mac Pro Intel “High Definition Audio” chipset? Has anyone done this with an iMac or Mac Pro? Has it made a big difference in the sound quality output? I’m currently looking into buying an external USB powered DAC + Headphone amplifier for my 2008 Mac Pro.
