Adapted from my post on another forum:
Indeed, a real stereo receiver and real (i.e., not computer) speakers gives you infinitely better sound than almost any PC speaker you can find, and this includes the "high end" PC speakers like Klipsch, top of the line Logitech, Midiland, Monsoon, possibly even Videologic/Sirocco, etc. Generally, PC speakers have atrocious sound quality.
If we're talking about maximizing sound quality vs dollars spent, nothing can beat headphones. If you don't mind wearing headphones (some people simply do not like it), you can spend a fraction of the price for the same quality of sound. Grado SR60's (arguably the best sonic value of all the headphones) cost ~C$120 or US$90 and humiliate most speakers under C$500/US$350. And that's without using a decent headphone amp or external DAC.
If, however, you absolutely must have PC speakers, I suggest going with 2.1 only, and rejecting digital speakers with their cheapo internal DAC's (if you want to use your digital out, hook it up to a real external DAC, otherwise, any decent sound card like the M-Audio Revo 7.1, Terratec EWX, or even the Audigy as a last resort). AC97 onboard sound is serviceable (spend it on the best analog 2.1 speakers you can get first, and if you have extra $, then upgrade to a nice sound card).
The Monsoon PM-14 2.1 setup IMO is the highest fidelity PC speaker that's not a Videologic/Sirocco (I also have the Klipsch 2.1's, which is decent, but a notch below). It needs a bit of equalization to sound its best, but you will be rewarded for your efforts. Every other PC speaker I have heard suffers from intolerable driver and enclosure resonance (usually any satellite with a plastic enclosure), colouring the sound to an extent no music lover could tolerate. The Monsoon's planar drivers and thin metal enclosures offer much less colouration than the usual crop of resonant plastic box satellites.
However, headphones or external receiver/amp + speakers would still be my choice.