I'm looking right now to find the ideal PCI and USB 5.1 or 7.1 sound device for the task. I haven't run into one yet that could not be used. I'll try to have a couple made and a couple ready to make at SELEM.
The outboard amp design is pretty solid. There might be a simpler way to do it, but this is very versatile.
http://www.akrobiz.com/laserboy/graphics/huge/laser_h_95.jpg
More details off this thread, if you like.
James.