Howdy,
A basking lamp has a couple of purposes; light and heat. No matter what, you want to have a nice bright light in addition to providing the proper basking temp. Many keepers find that a typical 75W halogen (halogen is whiter light per watt) flood lamp from your local Home Depot will produce enough light and can be positioned to create an 85F-90F basking temp. Skip the ceramic heater. It has the opposite effect that you're looking for. When it comes to typical incandescent lamps (and ceramic heaters) the wattage is proportional to the heat at a given distance. Look for ways to cool things down when not under the basking lamp. You want a thermal gradient from a high of the basking temp to something around 70F at the lowest point in the enclosure if you can. Nighttime temps in the entire enclosure should be allowed to drop to as low as 60F while 70F in the summer is ok. Remember, these are temperature goals that you are trying to accomplish that your critter will benefit from if you can do it.
A few more sources of info just in case you haven't seen them:
http://www.chameleonsdish.com/
http://www.chameleonnews.com/ especially
http://www.chameleonnews.com/ref.html
http://www.adcham.com/