Best antivirus thats easy?

So my office is gonna give up on Norton. Thank god!

But I am trying to figure out what is the best alternative antivirus out there that be good for work use.

ZoneAlarm Pro is an option since its an all in one package with firewall etc but I don't know how great is their anti-virus.

And what about reliable open-source antiviruss?

Please note, AVG sucks.
I can only gauge by the free version, from personal experience, but it's the lamest AV software Ive used in the last few years.
I use Avast! Antivirus at the moment, can't recomend it either way so far though.