If you're really paranoid, I suggest you try more than one Antivirus. I've tried AVG, McAfee, and several other free and cheaper Antiviruses. In my opinion, none of them were as good as Norton. (The rest seemed to miss a few rare viruses.) Also, Norton does a good job at scanning, and can constantly scan (the other can too, but not as good I think). I don't think it sucks as much resources as you say. It is a big program compared to the other ones though, so I see your point. If you have 32 Megs of RAM, then it would be a problem though.

Also, try another firewall like Tiny or BlackIce.