I have a BDP-105 that I run its stereo outs directly into my Lyr 2 and the sound is first class. The DAC implementation in the OPPO players are excellent so I would not initially jump to the Bifrost as it will not give you the same improvement as going to the Asgard 2. If you are using HDMI to connect to your receiver, then you are NOT using the DAC in your Oppo for HT multichannel sound. This would leave the analog outputs free for connecting to an Asgard. If your receiver has multi-channel analog inputs (RCA) and you will be connecting your Oppo with these then you will be using your Oppo DAC for multichannel HT sound. You can then use a Tape Output from your receiver or a Y-Adapter on the FL/FR outputs of your Oppo to connect to the Asgard for optimum sound. BTW connected this way, your Oppo handles the room surround setup not your receiver.
I chose the 105 as it gave me a Class A DAC with optimized dedicated stereo outputs for pure stereo use as well as the standalone capabilities of a separate DAC along with the functionality of the 103 series. Hope this helps.