IMO, the best setup would be to use a hardware NAT router as your firewall; Anti-Virus such as AVG or Avast. And a Spyware/Adware detector such as Lavasoft's Ad-Aware SE Personal

My personal advice is to not use multiple programs that perform the same function. (And some do not even do that very well.)

But the ones i just recommended all have good credibility and should be all you will ever need. (Be sure to keep them up-to-date too. )