Heres a good example. I just got a new computer.
I have onboard 7.1 sound on my Biostar 965PT and I thought it would be good. I listen to music alot and I couldnt tell in my RPG's. Yet when I loaded up winamp I was like ewww. I came from just a 5.1 Sound Blaster Audigy SE with 96khz sample rate and 24-bit.
I figured since I only paid 30 bucks for this card at walmart about a year ago that it wouldnt compare to brand new onboard. Yet its only 96khz sample rate and It blows onboard 7.1 away on a NEW chipset.
If your a gamer and play games that have high quality demanding games with loads of sounds like Bf2142 or so then i suggest going for this.
24-Bit and 192khz sample rate 7.1 audio
Not only will high quality sounds such as MP3's or BF2142 be noticibly different, as stated it will take the strain off your mobo to your sound card increasing your FPS. I would get that card for 50 bucks or get this one for only 30 bucks. I own the 25 buck 5.1 one and it destroys my 7.1 onboard in Mp3's and BF.
I highly recomend a cheap good sound card over onboard ANY day.