Avast is good. If you really Serious about server Security, go for Symantec or McAfee. Symantec is far better than McAfee when it comes to End Point Protection and DLP. But being unbiased i would recommend Symantec always. But its upto you how good deal you get from the vendor.
I don't know if this is surprising or not, but you're the first I've heard recommend symantic while being serious about it. It's laughed at in the hacker circles.
Yes that was the personal view you are free to disagree, i m not hacker to judge on that level. I talked about Symantec in the context of End Point Security and Data Loss Protection(Vontu).