Okay, I gotta get one more plug in for the Griffing Powerwave amp. This little gem is a Tripath Digital amp made for computer use- it's about the size of three CD cases stacked up. It as line in, mini-jack in & USB in- pretty much any way you need to connect it is okay.
The sound is stunning- well above the level you normally think about with Computer Audio. If your speakers can keep up, the level you need to compare it to is your main home audio rig. If your rig is a good one, that is. The Griffin is a soundcard & an amp, and it takes whatever crappy soundcard that occupies your PC or Mac completely out of the mix.
For $99, don't let this jewel get away. It's killer for computer use.