My MB has a Realtek ALC888, one of the better onboard chips available at the time. Surprising how decent it is, it would certainly "make do" for most.
But it's definitely not close to my old Audigy. Just through a pair of half-decent Sennheiser's it's noticeable.
But then the lack of driver hassle is even more noticeable.
In the end I decided not to bother getting sound card last time around, tipped over by the saving allowing for a step up in the CPU. Thought I might come back to it, but the basic competency of the onboard chip combined with the lack of hw acceleration support and memories of the hassles keeps me away.