Good Managed AV Software

I’m currently using Symantec Corp v 10 on Server 03 for a managed antivirus solution for about 50 XP workstations. We are looking for a replacement AV solution, and I thought I would check here to see what others might recommend. I would essentially like something with a small client footprint. I’ve thought of AVG, but their version 8 seems to be a bit resource intensive even without scanning.

What works best for you guys?