Will a rheostat or thermostat help increase heat output ..

[Tigergenesis]

in other words raise the temps?

[Hoomi]

No.

Using either device, all you're doing is controlling the heat source in one way or another. With a thermostat, it will cycle the heating device on and off in response to the sensed temperature. With the rheostat, you will limit the current passing through the heating device, which will in turn lower the amount of heat produced. Neither device will "boost" the power to the heating device, which is what would be required to get more heat out of them.

Important note!

NEVER boost the power to an electrical device beyond what it is rated to handle. A 10 watt heater will likely fail quickly, possibly catastrophically, if "pushed" beyond the 10 watts of power consumptiion. Overloaded electrical devices can melt down and/or catch fire, and many of the materials used in them can produce toxic fumes when burned. Such fumes may not do much to creatures the size of humans, but they could prove fatal to smaller creatures with more sensitive respiratory systems.

That said, here's the flip side of the equation. Using either a thermostat or rheostat will allow you to use a higher power heating device and control it DOWN to where you want it. If you're currently using a 7 watt UTH and it doesn't seem enough, you could pick up a 20 watt UTH, and using a rheostat decrease the effective heating of it down to, say, 12 watts. If you use a thermostat, you'll need to position it very close to the heat source, or else it will quite possibly never sense the temperature change and simply not regulate the temperature.

Obviously, too, if you go to a higher wattage heat source, be sure to take steps to prevent the snake from getting against any surface that might get hot enough to burn them.

[pimp_n_python]

hoomi's correct
increasing a load over what a device is ment to handle is a bad idea