SB Audigy 2 Value vs. Onboard HD Audio (MSI P55-CD53)

Doesn't hurt to try it, you have nothing to lose.
Btw i've tried it and found the Audigy2 sounded better! way better SNR and less noise.
The mobo makers listing onboard sound as 108db SNR are blowing wind.
I still haven't seen a test to prove otherwise.
High 80's db SNR is the best i've ever seen for onboard and THD and noise is terrible.
Case in point
http://www.legitreviews.com/article/1500/11/
http://www.legitreviews.com/article/1495/10/
Gigabyte boards generally have the best onboard sound.
That being said i have two with ALC 889 and both have soundcards in them now.

I personally ran into an issue with my setup... found out if you have 4gb or more ram you will have issues. My issue manifested itself in the fact I have no mic but the speakers work fine. Others report only getting 2.1 out of 5.1 speakers but their mic works fine. I contacted SB about it and after 6 MONTHS of back and forth emails they "escalated" the ticket and I never heard back from them. surprise surprise huh? Anyway You can try it but if you have issues with it try dropping down to 2gb of ram and see if that fixes the issues. I Just wanted to warn you that it might not be the card should you get the audigy and it not work right.