Panda is my recommendation
We dropped Symantec in the school for Panda. Easily installed and managed from the server. Auto updates daily whenever needed with no intervention. If your pc slows way down after installing, I agree with mrscott21 that you dont have something set right. Prices from Panda VERY good per year compared to others. They may still buy out your existing AV if you switch over. They did at one time.