good antivirus for 800 users?

I'm looking for a good antivirus program to use on our network of 800 user. I checked into norton corporate edition but we just cant afford it. Does anyone have any suggestions on cheaper solutions? Also I'm looking for a web filtering program, any ideas there? I am curently looking into cyber patrol and Symantecs I-Gear.

We use Trend Micro's OfficeScan Corporate package for AV. Was cheaper and has proven to be easier to use than Norton.

Nortons Corporate Edition 7.5 is the best I seen for networks consisting of several users but it does cost alot about $44 per license Network Associates may have something that can do the job cheaper

Thanks for the input guys. Network associates is still a little high priced for us, but Trend Micro seems to be pretty good.