Streaming 5.1 audio from a PC / Laptop has to be thru these options only :
1. Optical out (S/PDIF Out)
2. HDMI Out
3. Co-axial digital out
4. Analog audio out
Front Speakers output thru audio out 3.5mm jack
Rear speaker output thru mic 3.5mm jack
Sub-woofer output thru line-in 3.5mm jack
Now the complication is, in case of S/PDIF and Co-axial out, you have to stream audio
thru AC3 compression only, S/PDIF and Co-axial can't carry uncompressed audio data.
HDMI can, and HDMI is the latest standard.
But since you don't have that in your HT, you've to use a HDMI to co-axial convertor.
And that's available online with price ranging from 3000+.
So dude, that's about the gist of it.
Good luck !!!
PS : I suffered for a month, while searching for means for streaming 5.1 audio from my PC to my HT that has optical in only, as my motherboard had a S/PDIF out on board but not bracket or port (none is available easily either), i was stuck big time.
But found a way and it worked....worked like a charm and I'm in a bliss with superb 5.1 blasting thru my HT
PSS : I've never written such a long PS