I got my Phoebus running in Win 8.1 Pro , but the thing is that the Dobly HT software wont work with it though.
Edit: dont enable Xear Surround Headphone, it will disable the Phoebus Control center and make the soundcard stop working (Work around, inactivate sound device and reactivate it again).
They need to do an driver/softw update on this i think.
Edit 2: Removed Drivers + soft, Disabled UAC and reinstalled Driver package with Admin privilege, then it worked just fine, Re-enabled UAC again and it still works, seems that you need it disabled when installing.
(Got this tip from sh000kz (thx m8)).