Why is streaming sounding better than my DAC??

I have a VERY odd problem that just got onto my radar screen in a random way.

First, here's my equipment:
Coda CSib integrated amp
Ayre QB-9 DSD DAC
Auraliti PK-90 USB server
Buffalo USB 3 external hard drive
Dynaudio Focus 380 speakers
Audience Au-24 SE speaker cables
Cardas Clear XLR interconnects
Cardas Clear & Grover Huffman power cords
Wireworld Platinum Starlight USB
Apple Airport Express
Radio Shack stereo mini to RCA cable (for Airport)

The issue: Due to a random happening, I ended up listening to music streaming from my office computer (2009 iMac) onto the system above. The music on my iMac is either encoded AIFF or ALAC directly ripped from CDs.

The way my system is set up, I can switch from playing streaming music from my iMac to the system above with the push of a button on a remote. Out of curiosity (mostly to see how bad the streaming version was compared to the DAC), I listened to several of the same songs in 44.1 via both options. I was STUNNED to hear that depending on the song, there was either a negligible difference between the two methods, OR, the streaming version was better in almost every way: bigger (deeper) soundstage, deeper bass, same or better level of realism, etc.

I ended up installing Audirvana on my iMac and listened again....this made the differences between streaming and direct DAC even bigger. Thinking something was wrong, I plugged my Ayre DAC into my (old - 2007) Macbook laptop via USB in order to bypass the Auraliti server, which I thought might be the weak link in the system.

Comparing the iMac streaming vs the Macbook>Ayre DAC the differences were smaller, with an incredibly slight edge going to the streaming version. I even installed Audirvana on my Macbook, and I would say that while there are very subtle differences between the two methods, in terms of quality, the differences are negligible.

I have now tried many different file types, and the only way that the Macbook>DAC beats the iMac streaming is if I compare an HD file (e.g. 96) on my Macbook with the 44.1 encoded version streaming via my iMac.

I have had several audiophile friends over here that have loved the sound of my system, and know that Airport can only stream ALAC 44.1 versions of music.

So, finally, to my question: what is going on here? Why am I getting this result? What am I missing?

Thanks in advance for reading....and pondering.

Matt