This has been tested on Ubuntu 12.04.1 and 12.10 x86_64
I got myself a USB DAC and a set of nice headphones for Christmas. One of the main concerns was that the new hardware must work with Linux since Linux is my main OS at home. As it turns out most USB DACs work out of the box with Linux as they are standard USB compliant sound devices.
All modern Linux distributions seem to use pulseaudio as a front-end for ALSA these days. The thing that pulseaudio does is to remix all audio streams in software which is a bad thing if you have some nice audio gear that probably can do this much better.
The following explains how to uninstall pulseaudio and to configure ALSA on a per user basis. It also explains how to up-sample your audio from spotify, deadbeef, vlc and so on via ALSA.