How to change the default soundcard in Debian to an external USB?

Running Jessie and aplay -l gives me this:

The usb card is my only working device (alsaplayer -o alsa -d hw:2,0 rocknroll.mp3 confirms this)

so I came up with the following /etc/modprobe.d/sound file and restarted pulseaudio:

But still no sound on my system. What am I not doing? I had to create the sound file above as there was none before. So maybe that's an outdated way of doing things.