When the OPPO is set to LPCM it is doing the decoding of the audio tracks on the disc and sending it to the 990 which understands LPCM and does some bass management functions and sends that to the amp. If VUDU or NetFlix are coming to the 990 as bitstream you are depending on the 990 to do the decoding which it can do for all the older formats of DTS and Dolby. If the source material from streaming is set up for the newer formats the 990 may have some issues trying to decode them. Setting your OPPO to LPCM bypasses the decoding issues of the 990 and cures the problem. It also makes use of the highest quality DACs in your system. Those DACs are what make the OPPO 105D so expensive so you might as well use them. The best pathway is as described above to use the analog outputs from the OPPO to the 990 analog inputs and let the OPPOO do all decoding.