Can I Improve Sound--Macbook Pro as Music Server?

My system:

NAD M2 (amp/dac)
Audiphilleo2 spdif to usb converter
Macbook Pro (2012) /Furutech Formula 2 USB cable
Itunes- Tried Puremusic demo and thought it was actually less impressive than Itunes
Speakers: Mirage OMD 28

Files are all on the Macbook Pro- don't have an outboard drive yet

Recently switched to ripping in AIFF after starting off with AAC

My system sound lacks a little in weight / clarity/ resolution

What can I do do beef up / clear up the sound with my Macbook Pro?

What about the optional power supply for Audiophilleo2?

Thanks