Digital connections from pc to speakers?

[grendizer]

Hello,
I have a question to those who digitally connected their PC to their speakers.
I'm using the Logitech Z-5500 Digital 5.1 speakers on Windows Vista. For now, they are connected to my mainboard with the 3 analog cables.
I will soon purchase a HTPC and I would like to connect it to the Z5500 using a digital cable (optical or coaxial).
When I will switch to digital wires, the speakers can only decode AC3 and DTS. It cannot decode all other audio codecs, like for example , the "Ogg" audio format, DTS-HD, Dolby TrueHD, AAC, FLAC, or 5.1 streams from video games.
So through a digital connection, only these 2 formats can be sent to my speakers: DTS and Dolby Digital (AC3).
But I have heard there are some soundcards and motherboards that can convert all these "alien" audio formats to AC3 or DTS on the fly. These technologies are called DTS-Interactive and Dolby Digital Live.
I'm wondering if someone is using these technologies and is it working well?
Thanks
Grendizer