Perhaps a stupid question, .... but...

Are the benefits of programs like Amarra or Pure Music only evident when playing files already downloaded on iTunes (HD Tracks, ripped CD's, etc.), or can these "players" also be used with streaming audio like MOG ? The reason I'm asking is that I just discovered the amazing collection of music on MOG.com, and, so far, it sounds really good as played from my MacBook Pro (mid-2010) through my HRT Music Streamer II into my Rogue Audio Cronus and out of my Revel F12's (see my system.) Is it smart to purchase PureMusic or Amarra for MOG streaming playback, or is it a waste of money ?

And while I have your attention ...... for those of you familiar with HRT products, is the improvement from the Music Streamer II to the Music Streamer II + a worthwhile purchase ? Kevin from HRT says I can upgrade for $150.