(The following is from the Lowe's Website) Dimmer Switches "These specialty switches allow you to increase or decrease the brightness of an incandescent light to achieve the mood you wish to establish in a room. They come in single pole and three-way models and can be used for incandescent lights only. Dimmers can come with control knobs (rheostats), sliders or toggles. When choosing a dimmer, be sure that your fixture wattage does not exceed that which can be handled by the dimmer you choose. Three-position toggle dimmers can handle a maximum of 300 watts. Knob-controlled rheostat models can handle up to 600 watts. Dimmers often come with wire leads instead of screw terminals. A three-way dimmer switch has an extra wire lead which should be connected to the wire previously connected to the brass terminal (common) on the old switch. Only one of the three-way switches going to a light can be replaced with a dimmer."
You can have dimmer switches installed on the entire set of switches, using X-10 technology. Leviton makes a switch set rated for up to 500 watts, which should handle all of your 75w can lights. Check out this link: http://www.smarthome.com/2201.html