Hi guys. My current audio setup is using a USB sound card. The Creative X-Fi 5.1 USB. As of right now I have 2 monitors connected to the system. I want to add a subwoofer. The X-fi comes with a sub output but the problem is I need help with how to setup the subwoofer onto this soundcard. The second question is, should I connect the USB sound card via USB or the optical cable? Thanks a lot. PS. The sub I have is a mirage PS-12-90.