My roomie is a gamer and has two computers. The Synergy software enables him to focus input seamlessly between them, but the same isn't true of their audio. His 5.1 speakers from Logitech only have one set of analog inputs, and SPDIF has its issues.
I have drawn up a schematic for a USB-powered 5.1 summing box with 2 simultaneous surround sources. I'm going to get some PCBs made and he's going to pay me for it.
Anyone else want one?