Chris;

If electrical connections are all good and light output from incandescent Lamps is at max but still getting lost in the fixtures as Eric suggests, it's a fixture issue (reflectors or reflective surfaces? diffusers? etc)...and you cant simply increase the light by increasing the wattage because that will, as you suspect, increase waste heat which can damage things...so an LED solution might be interesting, but you would have to do some trial and error and engineering of the brightness control/current limiting. The trick is to use white LEDs at a current which will result in brighter light output, undoubtedly less heat than the incandescent but hopefully with more light to offset the losses in the fixture...they still MAY need some heat-sinking to shed their waste heat. Contact me directly if you want my help on this.

Cheers