A regular incandescent bulb gives out more lumens/watt the higher the wattage of the bulb. So one 300 watt bulb will give more light than two 150 watt bulbs, etc. So theoretically if you put 500 watt bulbs up there you could get away with less bulbs.
Long life incandescents produce LESS lumens/watt than regular life bulbs. A bulb rated for 130V run at 120V will produce 25% less light, use 10% less electricity, but last twice as long as the same bulb rated at 120V.
Halogen bulbs (which a version of incandescent) are more efficient that regular incandescents.
For real cost saving you need to switch to CFL or LED bulbs if you want to keep using the same fixtures. But the price can be prohibitive. What's the point of saving electricity if you barely save money when you factor in the cost of the bulb?
Let's blow your mind with these two opposing options:
http://1000bulbs.com/product/54730/FC100-35840.html
http://1000bulbs.com/product/104/IN-1500CLMOG.html
300 watt mogul base but 130V rating:
http://1000bulbs.com/product/5264/IN-0300PS35CR5K.html
300 watt medium base 120V rating:
http://1000bulbs.com/product/54906/IN-15737.html