Sunbelt Software Vipre Enterprise.
We used SAV, and switched to Trend Micro for a few years. We started with Vipre about 9 months ago, and are VERY happy. It's easy to administer, the client is VERY lightweight, and have not had any issues with Viurses.
I would highly recommend it!
http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/
They also have a home version, and sell an unlimited home licenses for $50. So one license covers as many PCs that you install it on in your home.
No, I don't work there...I just love the product.