OpenBSD/FreeBSD Firewall w/ GUI that is compatible with Intel 82574L Gigabit LAN NICs

Solution 1:

pfSense 2.0 has back ported Intel drivers from FreeBSD 9 so that will definitely work, and is generally the preferred release for new deployments anyway. m0n0wall snapshot versions should work too.

Solution 2:

M0n0wall snapshots (development version) are currently based on 8.2 and should support your NICs.

You could also use a full install of FreeBSD with Webmin for the GUI. I haven't used Webmin on FreeBSD, so I can't attest to the completeness of the interface like pfSense or M0n0wall.

Solution 3:

If the current pfsense or monowall won't do and you don't want to run beta or release candidate versions, you could grab the latest Freebsd or OpenBSD and use Firewall Builder. You won't get all the extras that monowall or pfsense provide, but if all you want is a firewall it will work.