I have never tried an airport express so I can not comment. I only have about 60 hours on my DAC2 but I have not heard much of a change in the sound yet, I am however getting more accustom to its sound.
Please post some comments after you hear "The Brick".
Cymbop,
Tonight I defiantly like the softer highs of the Wyred 4 Sound. My wife went out to a Backstreet Boys concert so I am at home listening much louder than my typical volume (just cause I can..) and my ears would have given up long ago on the Benchmark.
As I listen to my DAC2 I like it better and better but I really do not think it is any better than the benchmark, just a little different. I do not think the Benchmark has the best synergy with the Thiel line however. Thiels can get a little hard anyway so they do not need a hard front-end.