I am with Drauk. This may sound c0cky but the best AV / firewall software is not catching anything in the first place.
A router which does NAT (they practically all do) will protect you from *unsolicited* incoming rubbish.
It won't protect you from infected websites exploiting a back door in your web browser; running the very latest updated IE6, or running something like Mozilla (doesn't work properly with some websites) should take care of that one.
It won't protect you from infected emails, which will either exploit a back door in your email program, or will hope that you double-click on the attachment before thinking about it. Running a non-Microsoft email program generally plugs the former hole (although Eudora has been hit too) but only current AV software will plug the latter hole.
For a home user (not running a web/ftp server etc) a firewall will do no more than a NAT router for incoming stuff, and the only outgoing stuff which you will want it to stop is stuff which you have already caught and then it's too late for *you*.
I use current-patched IE6 for me, Mozilla for my kids, and a fairly rare email/usenet program. Never caught anything.
The real challenge today is stopping kids catching stuff. They click on every link on every website. I found 13 viruses the other day, on a PC dedicated to them (which also runs FS2004 for my instrument practice).
If you really want AV software, have a look at Kaspersky (.co.uk). It is the most compatible I've ever used; much better than Norton 2003/2004 or McAfee. I have built a lot of PCs and found K just works whereas the others cause havoc occassionally.