This may work, but I would go with one of the more flexible firewall solutions for Game PCs as well, unless you ready to "ghost" them fresh often.
Firewall you should be looking for needs to support DMZ, IP alias for public interface and NoNAT touneling option. This at last let you to protect the most exploitable services. Having no firewall at all for Game PCs is asking for trouble. There are many free or inexpensive solutions to your discretion. SME will serve you well as a basic firewall for office computers with integrated mail, mySQL, file/print, domain authentication etc. services or stand alone internal server behind firewall.