I have a retina macbook pro and I am considering creating a hi-fi system with it. I have looked , and pretty much decided that I was going to get a Marantz pm6004 and monitor audio bx2. Then i realised that 80% of my music is itunes downloaded, so is 256 or 192 kbps. Was wondering if i need a DAC to upscale this, or am i misreading the us of a DAC, or is it not neccessary