It's true, but be aware if it says it draws 35 watts of power, that doesn't mean it draws less than 35 watts. It might put out the lumens of a 50 watt bulb, but if it draws 35 then it draws 35.
35 watts is 3 amps at 12v.
In other words, if you can find a HID that draws 25watts, and assuming your original lights are 25 watts, then the HID's will draw the same power, but put out more light.
I wouldn't go above 35 watts without upgrading the existing battery or charging system, again assuming your current lights draw 25 watts.
You could also put an HID in the center light, but it would probably be easier to do the sub lights since they won't have low/high.