Soundblaster live value or onboard p4800 audio?

I replied to a post like this before. Bottom line: Why don't you try them both and see which one serves you better. Are you big on music? Compare them playing back different [high-quality] audio files (try some CDs). Are you big on performance in games? Compare the gameplay (or the framerate for that matter) on the two of them to see which does better in accurately positioning the sounds, having higher performance, better effects, etc.

I'd install the two of them together if there were no conflicts and compare them by alternating the cables and Windows' audio properties. This gives you a better feel for both.

Ah BTW, Live! Value is a 4.1 card while your onboard is probably 5.1. Is this important to you? The 5th speaker (the center channel) helps immensely in getting good sound from DVDs for example.