You don't really need an extra sound card for basic stuff. If you have good speakers, then you will hear the difference to a real sound card. Also a sound card has less load on the CPU, but I think that's negligible for today's powerful CPUs.
But you can disable the onboard sound if you want a sound card, that's no problem.
That board is an excellent board if you don't want to overclock. Intel boards aren't good overclockers (if you can overclock at all). So if you're not into overclocking it's a good choice.
All's right with the world when your PC is working right.