ogg 5:1 question

Hello,

I'm thinking to start using ogg 5:1 sound streams instead of mp3 stereo sound in my movies but wondered if:

1)This feature was well supported by ogg already
2)The resulting file will be much bigger than my stereo mp3 file
3)(the most important thing) I have spdif out on my sound card and wondered how I can make my home dolby digital decoder to distribute the 6 channels to my speakers (I don't have the decoder nor the speaker, so, if someone knows about a special hardware ogg decoder I would be happy too). As far as I can understand this won't work if my hardware decoder doesn't support ogg (and I don't think I will find one), so what about a way to "connect" the ogg decoder with ac3 encoder (by software I mean) then to give the resulting stream to soundcard ?

thanks !

John