Not sure why you would want to replace your Oppo BD 105?Since you have the Comet Plus you can run the Oppo into the Aux input on the Comet Plus (RCA) and eliminate the ARC preamp entirely, since the Comet Plus has a preamp built in and has RCA and balanced outputs. I would also try a digital output from the Oppo into one of the Comet Plus digital inputs to use its DAC section.
I love my Oppo BD 105 and keeping it! I'm running balanced outs from the Oppo into my ARC LS15 Pre Amp But in the interst of me getting into Hi rez Streaming, and taking my music quality up a level, I just purchased the Exogal Comet DAC Plus and I'm going to add the Zen Mini MK III streamer that can also rip CD's to an enternal HD
Brian Walsh