You have two options when dealing with notebook computer sound cards. All notebooks come with at least integrated audio and built-in speakers. The lowest-priced notebooks have the integrated audio solution. If you're interested in enhancing the sound performance of your computer, then you should look at notebooks that come with a sound card separate from the basic integrated audio. Many new computers, even some low-priced notebooks, are customizable and include a notebook computer sound card option to boost audio performance. New notebooks sometimes come with external speakers, other times they are available as an add-on accessory.
If basic audio is fine with you then there is no reason to add a separate notebook computer sound card to the new or refurbished notebook you are looking at buying. The same goes for external speakers. If you're not going to use them then don't buy them. Stick with the integrated notebook audio solution and the built-in speakers.