I have Just bought a Netgear ADSL modem router to replace my old hub, is the firewall in the router good enough to enable me to set the firewall on AVG to trusted, to enable the PCs to connect to each other.
Zonealarm is quite a competent firewall, provided it works for you (which it does for most people). I don't wish to denigrate it, but it has to be said that it is not the most fine-tunable free firewall available.
It has, however, been quite some time since I last tested it, and I have never used it in a network environment. For that, I always use Kerio. Perhaps a ZA expert could advise you how to get the most from it.
Whilst your router has it's own firewall it is always wise to use a software based one as well. Zone Alarm does do a good job, but does have some limitations with the free version.
Norton & McAfee are fine but can try to take things over. Suggest you stick with ZoneAlarm and see how it goes, if you need to upgrade then do so do the fee paying Zone Alarm, i use it and it works very well. In fact best thing i have spent on software in the last year.