I hated the fluttery background noises on the standard analogue audio jack on the RPi, so bought a Soubdblaster Play! for £20 from eBay.
http://elinux.org/RPi_VerifiedPeripherals#Class_compliant_USB_sound_cards said:
edit
/etc/modprobe.d/alsa-base.conf
and comment out the last line;options snd-usb-audio index=-2
I actually commented out all the extra lines that ended -2 and now I have excellent quality audio. Really pleased. The RPiBox is complete. Wires for the GPIO and an improved larger screen have arrived. I just need to find a container.