Kid
If you got a Genesis Lens, you could run both your Sony (as transport) and the Airport Express through it--it'll improve them both.
You wouldn't need as expensive a cable from the transport to the Lens--use your better cable from the Lens to DAC (though a better cable to the Lens will have some effect).
I have a new-found appreciation of my Lens after recently removing it from my system. Didn't notice too much initially, but putting it back in surprised me by how much more engaging the music was.
Along the lines of Mikesinger's comments, I was thinking of selling the Lens, it's cables (digital & power) and buying a better transport, but after this little experiment, I'm going to pass and keep the Lens for now.