Do you see the input and output bars moving in AC3Filter? If so it may be a problem on the receiver end maybe? The ALC1150 is listed as 8 channel, there is no way it can be reported as being only stereo capable unless maybe if you have like earphones plugged in.
SoundCheck reports Realtek Digital Output as 2 channels when in DDL/DTS mode. Can anyone who got it working check how many channels it is supposed to report?