I don’t believe Netflix and VUDU send anything but stereo to the PC right now. It is true, VUDU can use DD+, but they only send to connected devices. Netflix can also send DD+, but I believe that is only PS3 at this point.
Even if you were receiving the DD+ stream, you need the right type of GPU in order to bitstream DD+, otherwise, you’d be best decoding and sending as LPCM not transcoding to DD.