If you want high quality sound, every computer speaker [of which I am aware] is automatically disqualified. If you are serious about desiring good sound, put together a used 2 channel reciever(for the amp), a low cost subwoofer(such as the $125 Dayton 12" that is popular) and a nice pair of low cost bookshelves, like the Infinity Primus 150 or 140. Most sound cards today have some sort of bass management, so that makes it easy for you to route the proper signals to the satellites(bookshelves) and the subwoofer. If the sound card lacks this function, you can add an external active crossover, or you can get a receiver with built in bass management features.
-Chris