It depends on what quality are you expecting. Motherboards nowadays have built in audio that can support up to 7.1 surround sound. I am happy with 5.1.
If you have very high quality audio receiver & particular about sound quality, then yes. But if you are happy with typical 2.1 or even 5.1 speaker system that cost < $300. Then I do not think you have to spend anymore on a sound card.