ZooMed UTH pads are the way to go for heating individual enclosures. Flexwatt heat tape is the best for rack systems or stacked enclosures.
Whatever method of heat, a good thermoSTAT is a NEED! To recap - the ThermoMETER measures the temperatures inside the enclosure and digital with probe is best.
ThermoSTAT controls the output of the heating device, and better quality is a better buy. The best cheaper stat would be the Johnson or Ranco for @ $80.

Radient Heat Panels are a good source of heating, but they're expensive.

Lamps should only be used as supplemental heat to boost ambient temps.