Before I setup the server I had a Linux router/firewall on the front end connected to one of my two 10bit 16-port routers that I got for free at my previous employer (like I needed 32 connections, but they were free so...). I couldn't get my firewall to port forward for me straight away so I worked around it last night by installing a software firewall straight to the cable modem.

I'm just running one PC on this end now, and since it's running DHCP already if I lose my DNS connection I can always ipconfig /release and then ipconfig /renew. Still would have to update dyndns.org for the forwarding. Not ready to commit to a real domain yet...