Alan,
DMZ definition in the residential routers is misleading. It is not a "Protected subnet with limited access", but instead it is "Wide open host with no restriction"
If you use single public IP address for your Internet connection, you can only forward/map one port(or range) from public to private host for each service. Any SOHO router (including yours NetGear) will do it. Just forget its DMZ option (don't use it) and forward your HTTP (80) port to your internal Web Server, e-mail SMTP (25) to your mail server (could be the same as first one) etc... If your services are on the different servers, then forward appropriate ports to corresponding servers.