Personally, I don't think Avast is all that great. The last two Storm trojans I found were detected generically by an admirable number of other AVs, but not by Avast. If you have typical corporate users, you'll probably be wanting Storm detected, for one thing
When I had a corporate-type network, we used McAfee's enterprise stuff. ePolicy Orchestrator was nice. The AV client was rather CPU-intensive when all the bells & whistles were in use, and I don't think McAfee's detection rates or update rates are that impressive anymore either. Probably better than Computer Associates, though (and more expensive, I'm sure).
Who else has some recommendations?