No offence, but do you have _ANY_ idea how the sound travles from an mp3 stored on your disk to your ears?
I'll do my best. First, the media player uncompresses (if necessary) the file. Then the player may apply some filters (equalizer etc). How good are these filters? They affect the sound quality.
Then the digital signal goes through a DAC (Digital to Analog Converter), and ALL sound cards have one. What samplerates and bitrates can this converter support? What is the SNR (Signal to Noise Ratio) of the DAC? What are its distortions? Its dynamic range? These affect the sound quality.
Now from the DAC output we have a line-level signal. What can we do with it? Feed it to our headphones. But we want louder signal, don't we? So we need an amplifier. What is the self-noise/SNR of the amplifier? What are its distortions? What is its dynamic range? Do we use a pre-amplifier too? What are these specs for the pre-amp? Do we use also some hardware equalizers/other filters? Of what quality are these filters? All these affect the sound quality.
Now, finally, we have a signal strong enough to drive our speakers. What speakers are these? Do they have a woofer? What about mid-range and tweeters? What is the crossover for the woofer? Hardware or software based? Is the crossover frequency set correctly? Do we have the speakers set right? (proper height, proper distance from listening position, proper angle etc). Is our room acoustic-treated so it does not amplify some frequences and absorb some others? All these affect the sound quality.

I know I don't give the whole picture; I wanted to give you an idea of how many things can affect the sound quality. If you really want to look deeper, try to find some answers to the questions I have posted. Perhaps try looking into a Hi-Fi forum or a music recording forum.

yeah, i know there are many factors to influence sound quality, and maybe our "ears" are one of the factors also :D
basically, I think the current on board audio chips plus good quality 2.1 speakers will deliver good MP3 sounds to you.

Exactly. But what happens when you want to enjoy your vinyl rips stored in wav or flac? Then you need more than that to get the best out of it.
Also, regarding your original question what would you do if your onboar audio chip got fried? (I've faced it a couple of times).
Buy a new MoBo? Or a pci sound card for 20$?

I only want to play MP3 and CD,
onboard audio is sufficient.
A good sound card may cost more expensive than VGA card.

No, it cant.

HDMI is pretty much DVI + audio. It would be pointless to have a purely audio HDMI.

Its more than possible to have crappy sound via HDMI anyway.

In my experince, 'X.1' speaker setups arent that great. For sound quality, you would be better with a home stereo amp and speakers than most 'computer' speakers.

Warning- computer speakers are magnetically shielded. If you put 'normal' speakers to close to the box, you can do _bad_things_. As long as you have some space between the speakers are computer case you shouldnt have any problems.

'May' is not 'will'. You can get decent sound cards for less than any new video card, and even if you are looking for very good quality sound cards they are still a lot cheaper than a lot of 'gaming' video cards...

In Malaysia's market, Creative Lab's products are the most prevalent.
But I have long never bought its product since mobos come with sound chipset.
At this moment, I have a set of 2.1 Altec Lansing speakers.
It is not so good, it is a 3 years old product.

A smaller size speaker does not mean poorer quality than bigger size speaker, right? Like Klipsch, its speakers normally are smaller.

For this speaker system,
http://www.klipsch.com/promedia-2-1-computer-speakers
I think it is better to have a good sound card for it.

RMS is the real output power of a speaker, right?
Not the total power (200-300 Watts).
RMS 20 watts are considered very high power.

%&^$&$ creative, and the horse they rode in on. I'll never buy another creative sound card thanks to the mess they have made in the past. Asus is worth a look, if you ever do decide to get a sound card.

3 years old, 5 years old, just bought yesterday, there is not much difference between 2.1 speakers in any given price range.

http://www.klipsch.com/rf-82-ii-home-theater-system
This is my dreamed speakers, shall match with Denon/Yamaha/Onkyo AV receiver.

my AV receiver is Pioneer VSX model, like this one
http://www.pioneer.eu/uk/products/42...521/index.html

Smaller speakers can sound as good as bigger speakers. That doesnt mean that smaller speakers will sound as good as bigger speakers.

I've never heard them. That said, just because there is klipsch on the box doesnt mean they are going to be that great....I'd bet they have the same issues that all cheap 2.1 speekers have (buzzing in the sub woofer cabinet and distortion, in particular with the low end)

RMS = "Root Mean Square". Translated into non techincal english, its a continuous output number. 20 watts RMS is not that high at all.

i am not sure, but you may install a virtual sound devices that serve as a real sound card