Id try resetting CMOS on mobo, uninstall all drivers cleanly, check connections and start from scratch. I know I sound like a broken record repeating things but its the only way to eliminate the fault. Remove the sound card completely and try the green input on mobo.
Also soundblaster used to allow the option of providing you with a topdown view or 3d Image in the GUI where you could manually drag and drop/move the speakers around the central point to adjust the sound. You could then have actually put the left speaker on the right side and vice versa. I could do this on my old Audigy 2 soundcard to get the perfect sound placement for each speaker. It had separate config for speaker setup and headphone.
Also soundblaster used to allow the option of providing you with a topdown view or 3d Image in the GUI where you could manually drag and drop/move the speakers around the central point to adjust the sound. You could then have actually put the left speaker on the right side and vice versa. I could do this on my old Audigy 2 soundcard to get the perfect sound placement for each speaker. It had separate config for speaker setup and headphone.