All new here and I need some help

I am using jack together with brutefir to listen to music for a rather long time now on a dualcore atom machine. It handles up to eight channels without problems.

Now I want to kick the receiver out of my home-cinema setup and go for the brutefir way here as well. I just got a m-audio fasttrack ultra 8R, wich works out of the box with jack. Very good. The problem now is, that I use xbmc for video playback and xbmc simply has no option to output to jack. I had a similar problem with my audio-player and solved it using the alsa-bridge (alsa_in and alsa_out) to connect any alsa-based player to jack. The alsa-bridge is using stupid amounts of processing-power to convert even 48kHz input to 48kHHz output, which is total nonsense! I could live with that since I only had two input-channels. My video-setup will have up to six input-channels and I want to use the alsa-plugin this time.

Now I easily managed to set up a virtual two-channnel alsa-device which outputs to jack using /etc/asound.conf, but I can't figure out the syntax to create a valid 5.1 surround-device which xbmc needs. I used something like this and got two channels:

pcm.jack {
type jack
playback_ports {
0 systemlayback_1
1 systemlayback_2
2 systemlayback_3
3 systemlayback_4
capture_ports {
0 system:capture_1
1 system:capture_2
2 system:capture_3
3 system:capture_4


What I need is all of the 6 channels to be available seperately in order to route them through jack to brutefir and from there either directly to the outputs of the interface or through jack again and from there to these outputs.

Is there anybody around that would happen to know how to achieve this? I'd be so happy!

Best regards and thanks in advance!