I have 2 basks in my current Bearded Dragon enclosure. The enclosure is 4 feet by 2 feet and I am able to accomplish areas as cool as 75 in certain areas of the enclosure. You can use a much smaller wattage bulb for your second bask and still accomplish a great temp by simply providing an elevated platform.

My main bask hovers at about 140 degrees at its hottest area(50 watt halogen). The bulb used for my second bask is a 40 watt regular household bulb, however I elevate the platform high enough to get a pretty decent temp (120ish). With high temps on either side of the enclosure my cooler areas still stay around 75-80 degrees.

Check out Pro Exotics FAQ (Retes stacks section) and you can get a more visual idea of how to do this. Thanks.
-Ryan