hi , the fact is the stock airport express is very good but not as big Cd palyer or Drive , the reasons is , poor and noisy power supply , bad signal routing, bad ceramics caps on sensitive place and usual cheap clock.
what "Dan" do ( the more i know) is to put a double regulated and filtering power supply, rerouting signal on the airport express, add silver wires and lunndhal transfo for the digital out , a external superclock with it's own power supply, uppgraded caps on the airport card. ..
it is so good that i no longuer use an external dac with it .. ( my past dacs and CD players were Pass Labs moded D1, audio aero 24/192MKII and wadia 860X)
i have not the english words for describe the sound of the Zardoz but just ine word " Musicality"
i have two things that i will not change in my system, my SP tech timepiece 3.0 speaker and my moded airport express ZARDOZ.
cheers..