I only did the 35w kit in both, the 55w kits may need upgraded wiring and I definitely wouldn't put a 55w in the stock halogen fog light housing (it would probably melt it)
Stock bulbs are 55w. In addition if you remember high school physics class, since HID put out more light at the same energy level (wattage), there is less energy left over to be turned into heat.
55w will produce less heat that stock halogens, not more.
now wether its a good idea to put that much light out with other cars is a different story