The DACs I support in my software don't have any effects built in. All frame processing has to be done before sending them to the devices. The only disadvantage of the soundcard driver that DrLava wrote is a bit of lag due to limitations of the soundcard. But, it's small (100msec or so). This can be completely accounted for in software when playing back shows. Under live control it might be slightly noticeable but 100 msec is a very short time slice.
Some DACs have TTL or DMX output for controlling other devices like fog machines or external beam effects. A sound card doesn't have those but most likely you don't need them.