Depends really on your existing solution and what your intend to protect against.
If you connecting through a router, almost all consumer ones have a firewall built in and NAT will normally deal with the rest, ontop of that you also have windows firewall that is on by default (unless your firewall software disables it) and handles most known threats, so your already sat behind two firewalls. What software have you implemented and why ?
if you can do an envirment map of your existing infrastructure, we can probably get a good handle on what you already have and a small explanation of what you want to achieve, this would be great.
e.g. are you looking to shift all NAT and Firewall over to a hardware firewall / server.
In regards to the freindly network, that will basically be any network you mark as private or domain, it wont apply rules or monitor traffic (most likely) reducing cpu overhead, AKA you trust this network.
