Deltan,
I do have a comment regarding this subject. For a while I have contemplated what they call "active speakers". Basically these are (heavy) speakers that have the amps built into them already. In a lot of mixing studios, the little monitors that engineers use are considered "active".
What I like about the idea of an active speaker is that the amplifier and speaker combo is constructed to mate with each other perfectly. In that sense, the only thing that will really spoil the sound is whatever source component you feed to them (like a computer, CD player, or record player). So in effect, you dont have the problem of having too small of an amp for a big speaker, or having spent too much money on a powerful amp when your speaker does need that kind of power.
A sound card primarily delivers the audio signal in much the same way that a stand-alone CD player does. But like many items out there, they are built to a certain manufacturing price point, and they have many design compromises. The speakers that are delivered with a computer are usually junk. They use switching power supplies (usually via a "wall wart" plug) and tend to use the Class D style of amplification, which at its worst, is a very "unmusical" sounding experience.
