I read David Ranada (?) once did it, and many people thought it wasn't worth it. The idea is simple. Run the signal through a Dolby Digital / DTS receiver, then take the rears output and decode it with Dolby Pro-Logic 3 mode. That way you end up with 3 front channels (discrete) and 3 rear channels (matrix decoded). I doubt that's the way THX-EX is recorded, but I guess I could try it if it's worth it. Thanks! Javier.