SB X-Fi Surround 5.1 USB on Lubuntu

Solution 1:

First, delete your hack or else you will run in more and more problems.

Watch this question to see how you can configure pulseaudio so the sound come out of the right card : How can I change the default audio device from command line?

Solution 2:

The following solved my problem:

defaults.pcm.card 1
defaults.pcm.device 0
defaults.ctl.card 1

pcm.upmix51 {
    type upmix
    slave.pcm "surround51"
    delay 15
    channels 6
}

pcm.!default "plug:upmix51"

Thanks go to Trilby on the Archlinux forums in his response to Fluxed.