Does this PC build need a sound card?

You may want to get one. Some mobos have good onboard sound, so it is less important, but especially if you are gaming, you may prefer an add on card. One thing it does is offload some of the processing so that it frees up some board resources (same as what a vid card does). Granted, it isn't much, but gamers specifically are always trying to squeeze out better framerates where they can. 2nd reason is that often, onboard audio suffers from component noise. Buzzing or hiss at low level in the background. It really annoys me, maybe not you. The add ons often have better components that eliminate line noise. 3rd reason may or may not apply, but is just better quality and options. You can get surround and room effects that will be better than on-board quality.

The cons are that configuration can sometimes be a pain, and you may run into compatibility issues.

Most motherboards have built in soundcards capable of 5.1 surround and unless you're an audiophile, it should more than suit your needs. Just make sure your motherboard has onboard audio. Good Luck!

The integrated will be fine.