I had a friend recently install an ASUS ROG Xonar Phoebus Solo in my PC (MSI Gaming GTX 780m, SSD and HDD drives, 16GB RAM etc), which now is plugged into my AV receiver via SPDIF (optical), and that receiver supports my 5.1 speaker system.

The issue I am having is that launching FFXIV, all I am getting is stereo output out of my front R and L speakers.
Games off my STEAM account (Batman Arkham City, Borderlands 2, Dishonored) all have the surround sound active, just seems to be FFXIV ARR.

Anyone else had this issue? And any way to resolve?