All the pieces must work together and not be too heavy.
RESEARCH YOUR SELECTIONS and see if anyone notes a problem with toxic combinations. For example I no long bother with Spybot or Teatimer due to some toxic combo issue. This is not an offer to tell which one it was but to help you find your answers.
Dell computers told me you can have too many spyware/antivirus protection. They claim these programs interfere with each other. Do you believe this to be the case?