Volume level doesn't change if the audio renderer is not the default sound device?

[diibadaaba]

TV-Server Version:
MediaPortal Version: 0.2.3.0
MediaPortal Skin: Blue Two Wide
Windows Version: Vista Business SP1, 64bit
CPU Type: C2D E6850
HDD: WD 1TB
Memory: 4GB DDR2
Motherboard: Gigabyte GA-P35-DS3
Video Card: Nvidia 8800GT
Video Card Driver: 174.74
Sound Card: X-Fi XtremeMusic
Sound Card AC3: Optical out
Sound Card Driver: 6.0.1.1304
1. TV Card: -
1. TV Card Type: -
1. TV Card Driver: -
2. TV Card: -
2. TV Card Type: -
2. TV Card Driver: -
3. TV Card: -
3. TV Card Type: -
3. TV Card Driver: -
4. TV Card: -
4. TV Card Type: -
4. TV Card Driver: -
MPEG2 Video Codec: FFDShow rev. 1846 (Feb 05/2008)
MPEG2 Audio Codec: FFDShow rev. 1846 (Feb 05/2008)
h.264 Video Codec: FFDShow rev. 1846 (Feb 05/2008)
Satelite/CableTV Provider: -
HTPC Case: Antec P182
Cooling: Noctua
Power Supply: Seasonic S12II-380
Remote: MCE Remote
TV: Mirai 32"
TV - HTPC Connection: DVI

My audio setup for tv is X-Fi optical out -> DAC -> power amp -> speakers. For general computer use and gaming I have a pair of Creative T40's. T40s, ie. X-Fi - Speakers needs to be my default audio device so that games and browser and so forth make use of them.

In MP I have Direct Sound: SPDIF Out as audio renderer. However the volume levels don't change if I keep the analog out as default windows device. Volume slider in MP moves, but it has no effect. And if I change X-Fi SPDIF Out as default windows device the volume levels change as they should in MP.. but then I lose my desktop speakers.

Direct Sound SPDIF or just SPDIF in MP settings doesn't make a difference, I've tried. Any ideas?