I have the following components for my bedroom:

1. PC
2. LCD TV
3. Speakers
4. HD DVR


This is how I plan on setting it up:

http://img143.imageshack.us/img143/2258/58305934kg7.jpg


Just a few questions:

1. Will I get 5.1 sound if I connect the PC and Speakers by a 3.5->RCA cable?
2. Will I get 5.1 sound when I watch 5.1/HD TV Shows if I go with the setup on the top? Or will I have to connect the HD DVR and Speakers with a Optical TOSLINK cable?
3. Are coaxial audio and optical TOSLINK audio connections basically the same?
4. Should I go with the Onkyo S3100 (http://www.newegg.com/Product/Product.aspx?Item=N82E16882120085) for $250 or Sony D (http://www.walmart.com/catalog/product.do?product_id=10199392)DWG700 for $180? The system will be used for my bedroom and I'd like to keep it with me even after I move out to an apartment where it will be used for the living room.
5. I might consider the Sony CT100 soundbar, figured I'd ask here also. Does the sound still good if I stand off to the side of a soundbar or do I have to position myself directly in front of it to get the same quality?
6. What is the HDMI connection good for for audio? I thought it's mainly used for video, why would I having it in a receiver be used for?

You need to post the specs of your sound card before any one can determine what kind of sound you will get....also....if your DVR is ethernet ready you might want to run a connection to the PC for that also.

I'm using onboard audio from my motherboard (Gigabyte DS3L (http://www.newegg.com/Product/Product.aspx?Item=N82E16813128059)).

Specs from the motherboard websites says that it's a Realtek HD Audio

1. Realtek ALC888 codec
2. High Definition Audio
3. 2/4/5.1/7.1-channel
4. Support for S/PDIF In/Out
5. Support for CD In