d71146,
Welcome to Mac! This is my 20th year of using Macs and I've never used antivirus programs and never had an problems with viruses, spyware or malware. There have been a handful of "proof of concept" viruses which spring up from time to time, but they are usually created by those with an interest in selling antivirus software and never make it beyond the lab. In my experience, antivirus programs on the Mac cause more trouble than they are worth, looking at the damage they have wrought on other people's Macs.
Incidentally, the firewalls on all my Macs are switched off - the built-in firewall in my router is enough.
Binos: congratulations on your ever-expanding portfolio of Macs!
Applemacster