I have 3 systems (ranging from entry level all the way to cheap) using that and I luv it, you will too.

It's a great setup and has no right to sound as good as it does with even a modest DAC attached to an Airport Express.  I'm getting great results with the "-G" AE, a Music Hall DAC 15.2 and a $3.81 optical cable I bought on Amazon.

I'm also playing around with Spotify (premium account, so up to 320 Kbps) streaming to the Airport Express using a program called Airfoil that lets you stream to one or multiple Airplay device(s) without using iTunes.