light bars don't increase long range and like HID's are not the ideal light for the human eye. It will open a can of worms, but a good halogen is still the best (in my opinion of course). They do however light up the immediate area well, the 10w are the go but much more expensive that the 3w ebay jobs, although I do run one on my farm ute and it does the job.
If you want to turn light into day try a set of fyrlyts 250's..
Yep, they can get you for anything, including having an empty window washer bottle if they want! Hunting lights on roofs are illegal, any rearward facing white light that can be switched on without being in reverse (like work lights) there really is very little you can do without pushing some law