Question for a HT on PC setup.

[wrong]

I am using this for my PC room which is big enough.

I have a setup question:

I am using

Marantz NR 1403 5.1
the PS500B 5.0 CH energy (EF500 tower x a center, and 2 satellite ES 350)
and EW-100 down firing sub.

My problem is the purpose for this HT is for my ps3/ TV/ and mainly for PC.

So i have a few questions here.

1. Does my soundcard matter? I am using a sonar DG from asus which i use my ATH-50 headphone with usually.

2. Should i get a DAC in between the PC and receiver?

3. Should i use my receiver for headphone or a DAC for headphone?

4. Does the speaker filter ever matter? Should i remove them ? I mean you know, a computer room tend to be a lot more dusty.

5. Since i am using tower speakers, i am a bit worrying about the power output of 50 watt of my 1403 into them.
I believe 1403 can have pre-amp which i am vague on that ideal of what it is. What type of amp i can do pre-amp on it?

 

[wrong]

It might sound like my last question, i am just confuse about it, because i read someone mention adding a DAC between PC to receiver can convert the sound better into 5.1.


Currently, i am running many issue with my setup.

I brought an output digital cable, only found out that it only does PCM 2.0 i can't get it to output 5.1 at all.

Secondly, i use my Radeon 5850 HDMI output only to find it disable my 2nd monitor, i am thinking buying a displayport to enable it back.

and thirdly, It flicker my monitor using HDMI whenever i turn the power on/off. Which is annoying when i switch source and back, it will also disable the HDMI audo from PC until i restart the receiver on/off again.