Sound Cards and Sound Editing

How much of an effect will my sound card have on my ability to edit sound files? I recently bought Cool Edit 2000 to clean up some old tapes I have, and I'm thinking about buying the audio cleaning plug-in for it. This is not really critical stuff. Most of it consists of lectures. I'm just trying to get the hiss, pops and clicks out of them. But I read somewhere that the quality of your sound card will affect how good a job you can do with this stuff. Right now, I'm doing all of this on my laptop, that no doubt has the sound on the motherboard. Not exactly high quality stuff. Just curious.