Simultaneous AC3/DTS passthrough & stereo analog output

[Bob <spam@homeurl.co.uk>]

I'm using an Audigy2 in one PC and an SB Live value in another and I 
output to a 5.1 speaker system over S/PDIF coax and to my headphones 
(via the TV) over analogue stereo.

I have AC3 passthrough working when I call mplayer with -afm hwac3, (I 
think DTS will work but can't find a test clip) and I can soft decode 
and downmix the AC3 audio with -afm liba52, so that's all great, except 
that with -afm liba52 rear left and right are mixed and I don't get 
anything out of the LFE track.

What I can't do is both at once which would make life easer for SWMBO.

My google search (below) has reviled I'm not alone in wanting this and 
hints that it may not be possible but my search skills are week so I 
thought I'd consult the oracle.
"ac3 passthrough" "analog (output | stereo | downmix)" (simultaneous | 
"both at" | "same time")

Has anyone got any suggestions on how to get this working?

Thanks for any help.