Most motherboards include on board sound. They can range from 2 channel up to 8 channels depending on the motherboard. Some include SPDIF (COAX or Toslink optical out) as well. You can however upgrade your sound card to achieve better sound results or to do features that on board sound cannot do. You should plan ahead and figure out if you only 2 channel, 4 channel, 5 channel, or more depending on how you want to control the speakers in your car. A common question that arises: Should I use onboard sound or an upgraded PCI or external soundcard?
External USB Soundcards
External Firewire Soundcards
PCMCIA / ExpressCard Soundcards
Audio Tuning via External DSP