Don't think i've got a virus, just nice to know i've got protection..
If Sophos is decent i'll stick with it..
Cheers.
I wouldn't even worry about an AV. There's not any known viruses for OSX and only a few bits of spyware and malware, all of which are near impossible to find let alone get infected by. Just get a firewall, I recommend Little Snitch, and then if you do somehow get something that doesn't really exist you'll know about it before it can become a problem.
http://www.mac-forums.com/forums/switcher-hangout/209182-official-antivirus-malware-firewall-faq.html