Background: I have tried to use routers, but so far all of them can't handle the bandwidth, number of connections eventually limited by the hardware resources, so overall the home routers are decreasing the internet speed. I went through DD-WRT and stuff like that.

Question: What I want is to use my Windows7 PC as router. It has 2 LAN cards. I'm going to connect to this router another desktop 2 pcs and notebook through wireless router. The main question is what is the most efficient way to turn this Windows7 box(and I need Windows for native NTFS support) into router with NAT/Routing/Firewall functionality?

Is there any routing software recommended for this purpose or I should just use windows native "Internet Sharing"? I'm going to run SIP phones in the LAN, so I need friendly NAT(Full cone perhaps). Also I'm going to have FTP server on that Windows7 "server" PC.

As firewall I'm thinking about Comodo. Need to drop all incoming, unless explicitly allowed.