I'm not an audio engineer, but running the radio station and also doing studio recording on and off, I have a little bit of knowledge about sounds cards. You have to think along the lines of how much better on-board audio has become up until this point as opposed to when it first starting appearing on motherboards; that's the reason why the market for sound cards is really tiny now, meaning that on-board audio is actually quite good for most purposes. Another thing to consider is that in the end every penny matters, and if the manufacturer can skimp on EMI shielding because 99+% of their customers aren't going to hear any difference, they'll go ahead and do it to because they have to compete with the other board manufactures. I'm starting to see higher-end motherboards with EMI shielded audio codecs and built-in headphone amplifiers, but without having a board with these features I cannot comment on if it's worth paying $200 to almost $400 for a motherboard. Some motherboards now come with a plastic condom that sits over the PCB, which I think is really fucking stupid because it's going to trap heat in and shorten the life in the board, when it's marketed to do the exact opposite! So what if it protects against EMI? There are motherboards still operating today that work just fine from the 80's without the condom!
Anyhow, as far as sound cards, any aftermarket sound card from Sound Blaster, ASUS, etc., is just more junk. Yeah, it'll sound better than on-board audio, but if you're really into wanting something that's of studio quality, studios do not use any of the aforementioned. My rule of thumb is that anything with a 3.5 mm jack is going to be junk. Both channels are squeezed down to having the left and right audio channels on the same connector. That's just an audio no-no for anyone who knows two shits about audio engineering. Can you imagine the end result you'd get if a professional recording studio hooked up their mixing consoles to DSP's and Pro Tools via 3.5 mm jacks?! The people who think Sound Blaster cards are so wonderful and record their guitar licks into their PC have to remember that the ADC and DAC on a Sound Blaster card is not going to be that great, along with the overall design of the card. Something like this, below, is where we start getting into sound cards that are going to be worth the money:
http://www.m-audio.com/index.php?do=pro ... interfacesHere's a picture of a high-end sound card made by Digigram for studio use:

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You can tell just by looking at it that it's not junk, like a sound blaster card. All it takes is your eyes. So, in my opinion, the difference in audio quality between Sound Blaster and on-board sound isn't great enough to justify buying a separate sound card unless it's one designed for studio use, and they're really not that expensive. And no offense, but the USB sound card that you gave a link to with the piezoelectric speakers looks really quite sad, like it would be fun to see how fast it melts on a hot dashboard in a car.