Multiple sound cards

OK, this is not strictly an X question...

I have a system with 3 concurrent users - a three head system - and I would like to provide sound for each one.

I have the hardware available, I just don't know how to configure the system so that seat A gets card A and seat B gets card B, so that the sound is always coming from the right set of speakers...

In other words, when a user logs in using ServerLayout Seat1, I want to always assign SoundCard1.

Anyone know of a way to do that?

Thanks,

--Yan
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