The differences in the files you present are too subtle for people to appreciate what a big difference DACs can make.
Try searching on Itunes for the following song and play the free sample:
"Nein, Mann!" by Laserkraft 3D.
Playing through my UDAC 2, the conversations, sounds of glasses etc. in the room in the background are vague.
Through my AMB Gamma 2 DAC, the same conversations come through crystal clear and crisp. The song sounds completely different.
PS I don't like this song - it's just a good resolution / noise floor test for DACs 
Edited by Bacci - 3/8/11 at 7:57am