yo dude,
to connect a 5.1 or 7.1 speaker you need a sound card that supports it. In-built sound cards dont support this feature (yet). so go for a sound card which ranges around 2500 (Sound blaster live). and as far as speaker goes i have heard that Creative or Altec Lansing is the best. However i use Mercury 5.1 and it does a good job for me. hence i stick with it and it doesnt cost a bomb shell.
just connect this and have 'blasting' fun