Free Anti Spam Software

I have had problems with bit defender, AVG, and Norton.

I manage a network that is made up of 1 file server running Windows Server 2003 x64 and 8 workstations running Windows XP Professional. I currently use Symantec Antivirus 10.2 and Norton Antivirus. I am thinking about switching to McAfee Total Protection. Has anyone used this product? I want to be able to manage all pc’s from one location (the file server). I’m not interested in anti-spam or firewall proctection. I already have that taken care of… just antivirus. McAfee sounds like it is cheaper and a lot easier to add additional licenses. I can purchase a minimum of 2 licenses versus a minimum of 5 with Symantec. Are there any performance issues? I know Symantec can be a memory hog. How does McAfee compare? Any help would be greatly appreciated. P.S. I’m only interested in these two products. I’m not interested in AVG or any other type of AV. Thanks.
Yes I have checked out the TOPS service. That’s what I was leaning towards. Thanks for your help guys!

I’ve been looking all over the place and I have tried avg and avast (are these good?), but extremely slow. I want a great free one that has no spam, spyware, or anything else like that. Thank you for all of your time and patience on commenting this.

I already know of AVG and Norton isn’t good. Anything else I’m missing?

Im using AVG free and its terrible. It never picks up anything and my computer is running slow and crazy. Whats the top of the line free protection????