There is no absolute answer to this question. Basically: No. Almost all modern PCs today have a good quality sound chip integrated that passes on good quality to the soundbar. What this sound card does well here is its truly outstanding sound chip and the setting options for the output. The card also has a TOSLINK (optical cable).
So it depends on what you want and are looking for. If you just want to play some music, you probably don't need the card.

No, a PC has enough connection options as it is.