You can lower the output level from the AirPort Express if you play from iTunes on a Mac or PC using AirPlay.
In iTunes choose Window > Equalizer and set the "Preamp" setting to "-12 dB". Remember to click the equalizer "On".
It takes a few seconds before the new setting is active.
I have the Libratone Live, but I bet this applies across the board. Thanks Libratone :) I was pairing 3 Live'(s) and one Lounge, and even at lowest volume I was getting the full ordeal!