As far as I'm aware there isn't really a drop in replacement yet. Hostguard appears to have fallen off the face of the earth, not seen any updates in months.
I know there are a few things in the works so may have more options later in the year.
When I was a bit younger I used to run NT4/Server 2000 with a domain and active directory at home! Overkill doesn't really cut it, but was a great way to learn.
Much more simple now:
Asus RT-N66U Gigabit Router
BT Openzone Modem (80Mbps down / 20Mbps up)
HP Microserver N40L, modded with 6x...