I'd say "cost-prohibitive" and thus impractical. The problem with an outboard conversion unit that would take multichannel PCM or digital bitstreams (DD+, TrueHD, DTS-HD MA) from a Blu-ray or HD-DVD player and output multichannel analog is the complexity involved. You need a DSP section that can at least provide things like bass management, time delay, channel calibration, and AV sync adjustment - and probably also some matrix processing modes like Dolby EX, DTS NEO:6, and Pro Logic IIx for cases when the source is 5.1 or less (there are and will continue to be discs that only offer two channels because that's how the movie was originally mixed) - because most multichannel analog inputs bypass all of these functions in a surround receiver or processor. If you include HDMI v1.3 support, you also need that DSP section to support decoding Dolby Digital Plus, Dolby TrueHD, and DTS-HD Master Audio. Then you need DAC's for all eight channels. You also need to make sure the device handles HDCP properly so that it can both establish a handshake with the source and pass the HDMI video on to a display. Consumers may even expect you to have more than one HDMI input on such a device so that you can use it with more than one player (perhaps a Blu-ray player, an HD-DVD player, and a universal DVD player like a Denon or Oppo) to make best use of the significant investment we're now talking about, at which point you need some switching control too. It makes more sense to simply take care of the audio processing in the player and output from there as multichannel analog or to replace the pre/pro with an HDMI v1.1+ model.