Greetings,

Pretty much any amp can be hooked up to a pc, using the output jack of the sound card to a rca input of the amp. The quality of this sound, as well as background noise, will vary greatly depending on your computer and it's card. Some amps/receivers(Outlaw RR2150 for one) today have a USB input, so you can bypass the sound card and hook it up that way. You will have no background noises this way. One note though, you can hook it up via usb OR sound card, one or the other, not both at the same time.

But, since you're looking for a 5.1 setup, forget the RR2150, you'll have to get a home theater type receiver or amp.....there's many different models in all price ranges. Any decent amp can handle 4 ohms speakers.

Good luck !