Sound cards are a waste of money these days. Especially if you have a high-end motherboard. This has been the case for the last 6-8 years.

Off all the people I know who actively build computers (professionally and personally) NONE use separate sound cards in their rigs (unless requested). I had the same questions as you a few years ago and it was unanimous. It's costs practically nothing for motherboard manufacturers to add high-end audio (5.1 or 7.1) to their boards. Thanks to competitive pressures, they all do it now.