Full surround 5.1ch effects SPEAKERS

[Markwinstanley]

Im planning to buy new speakers for Full surround 5.1ch effects.i want to take full advantage of DTS HDMA audio Movies and Music Videos.Following are my quires
1 what kind of Sound card will be best
2 What kind of connection will be of Sound card and Speakers like HDMI,Coax,RCA
3 What is sound receiver and its benefits
PC config
2gb ram
2.88ghz dual core
1tb hard drive
1gb graphic card