Something

#This asoundrc is a template to create a file that will upmix 2.0 (stereo) files to 5.1 speakers.
#It will also playback real 5.1 sounds, on 5.1 speakers, and also allow the playback of both stereo and surround sources at the same time.
#It may not work out of the box for all cards. If this is the case with your setup, please speak to me (wishie) in #alsa on irc.freenode.net

# 6 channel dmix:
pcm.dmix6 {
    type dmix
    ipc_key 1024
    ipc_key_add_uid false
    ipc_perm 0660
    slave {
        pcm "hw:0,0"
        rate 48000
        channels 6
        period_time 0
        period_size 1024
        buffer_time 0
        buffer_size 5120
    }
}

# upmixing:
pcm.ch51dup {
    type route
    slave.pcm dmix6
    slave.channels 6
    ttable.0.0 1
    ttable.1.1 1
    ttable.0.2 1
    ttable.1.3 1
    ttable.0.4 0.5
    ttable.1.4 0.5
    ttable.0.5 0.5
    ttable.1.5 0.5
}

pcm.duplex {
    type asym
    playback.pcm "ch51dup" # upmix first
    capture.pcm "hw:0"
}

# change default device:
pcm.!default {
    type softvol
    slave.pcm "duplex"
    control {
        name "Software Master"
        card 0
    }
}