Oy....the problem with this argument is you begin to delve into subjective perception of "hi-fi," audiophile, and low-end stuff.
As a generalization (and this is just me being honest), 99.5% of all computer speakers (IE: Klipsch PM5.1, Logitec z560, Crossfires, Monsoon MM2000, etc.) are pretty much utter trash compared to a true audiophile system. I would call them mid-range systems, and some of the cheaper ones I'd call low-end systems.
Are they loud? Well, sure they are. Are they nice sounding? Sometimes - depending upon what you're listening too. Do they compare to even a low end audiophile set up? No chance in hell.
One problem is the very output of soundcards - the DAC and ADC are usually of fairly shoddy quality even on the supposedly "high end" PC audio cards (IE: TB, Audigy, AE, etc.) - and you have to take in mind that a computer is a very electrostatically noisy environment where signals can be altered by other system components. The problem is compounded when you have high fidelity components externally (IE: amp/pre-amp setup, excellent speakers, quality cable) and things like that start to become very apparent. Until they start offering cards that actually have DAC's that aren't trashy, and remove them from the noisy computer environment, having a hi-fi speaker setup is sort of a moot point.
My father has a Rotel amp/pre-amp set up, a marantz CD player (*very* high quality DAC), and Vanderstein speakers, and about three hundred dollars of high end cable. This system absolutly blows away anything else I've heard outside of the shop that we bought them in - and when we hooked a computer up to it (with a decent card - a turtle beach), it was blaringly obvious that it was a computer. There was slight amounts of backround noise, and the overall signal felt a bit flat compared to the marantz CD player. I'm sorry to say that a computer doesn't even remotely begin to compare to a high end system, although there are components that have high quality audio, but they cost so much that you have to ask if it's not just cheaper to buy a nice stereo.
I'm not saying it'll never happen - but computers are still a *long* way off from audiophile sound.