Jon,
The Technivorm model I have retains 4 ounces of water from each brewing cycle. I put enough water for two cups of coffee into it, and run one cycle without coffee. That preheats the stainless steel caraffe. Brewing even two cups is not a problem.
There is an advanced technique for smaller quantities in which the user starts the brewing process, and turns off the valve on the cone for 30 seconds (suggested times vary from reviewer to reviewer). That allows more contact time. After 30 seconds, the user changes the switch setting, and allows the water to start flowing into the caraffe. This approach is dangerous for people who forget to change the switch setting, but with only 2 cups, the cone will not overflow even if the user forgets to change the setting.
A technique similar to the one described above is mentioned in the tip sheet at:
http://www.sweetmarias.com/prod.technivorm.phpThe Technivorm is very entertaining to watch. The water travels vertically in the tube, and a pleasant gurgling sound is made.
