Whta should I add or delete in the way of security software?

I have Computer Associates anti-virus and firewall, Spy Bot, Malwarebytes, CCleaner and ATF cleaner. I used to have Ad Aware, but it bogged down my computer so much, I deleted it. Malwarebytes never finds anything and its Quick Scan takes about 15 minutes - full scan takes almost 2 hours. The same with Spybot. My CA usually snags a few low threat items a month. I just want to know what I can get rid of and what a real must (free of course) to have installed. Thanks.