Saki,
I just bought an Oppo 105 and can tell you for certain you can use the unit as a processor and a limited input preamp.
Right now, I have the 105's 'Dedicated Stereo' xlr outputs connected directly to my main amp's xlr inputs. I also have the 105's 7.1 channel analog outputs connected directly to my 2 ht amps via rca cables in a 5.1 configuration.
If you set the 'Stereo Setting' to 'Front L + R' in the 'Audio Processing' section of the Startup menu, the Oppo has a unique ability to play back in either stereo or multi-ch automatically based on the inputted signal. This means when you play a CD it will playback in stereo and when you're watching tv or a movie, it will automatically playback in multi-ch surround mode.
I found I no longer need my tubed VTL preamp for music or my Parasound AV2500 for surround processing once the 105 was installed. I'm probably going to sell both to a friend for about the same cost as the 105 ($1,200).
The 105 sounds excellent for both 2-ch and multi-ch in my system. You may also find this simplified setup may work very well for you for both, too.
Before I sell my beloved VTL, I'm going to incorporate it back into my system just to make sure. I'm going to hook it back in between the 105 and my amp via the 105's 'Dedicated Stereo' rca outputs since the VTL has no xlr inputs. If it sounds even better, I'll leave it in. If not, I'll sell it as planned.
However, I seriously doubt I'll be able to improve on my current sound performance. I'm using the 105's excellent Saber dacs for decoding both ripped cds and hi-rez computer audio files and thoroughly enjoying the quality sound for both music and ht.
Let me know if you need more info,
Tim