If you just want an AV for sigs alone to combine with VS, NVT, CF Avira free is a good choice probably one of the best because you haven't got any zero day protection in Avira free that could conflict with your main zero day protection. But Avira Pro AV has a very good cloud and you can pick it up cheaply. But WD is perfect to team up with some solid zero day protection. If you go into group policy editor and manually change WD settings it becomes an extremely good layer of protection. I did some testing with WD tweaked via GPE last week and I was very surprised at it's protection it was impressive.