What advantage is a driver for P7 maglite?

I did a search and read throught a couple mag topics. I hope I didn't miss what I am asking now. I'm looking to put together a P7 maglite. I have a couple mags laying around. I've seen them done in a 3d with no driver. Is it going to be as bright as one with? Also can it be run on 4 nimh? Also where is the best place to get a heatsink, emitter, and possibly driver?

For flashlights of P7-level, multiple levels get really useful. Its easy to totally kill your night vision by illuminating something only a few m away (talking about "seeing spots" ruining here).

Also, your 3D just kinda works. A 2D would be a different story...
Having a driver enables a lot more freedom of battery choice.

A driver will enable actual non-dimming regulation as opposed to relying on the batteries ability to hold voltage as they're drained. Also you'll be able to drive the LED reliably to full power so 900 emitter lumens is no longer a "on a good day with just the right battery voltage" figure. There are a couple P7 drivers but the ones I've seen are sort of cobbled together drivers for other leds and not engineered specifically for a P7. Multimode would actually be handy in a light this bright (I usually say poop to those darned morse code switches but for an emergency/non-tactical type of light it would be a good idea)

Anyone know where the best place to get the p7 and heatsink?

Here is cheaper place to get heatsink:
http://www.cpfmarketplace.com/mp/showthread.php?p=2166815#post2166815

Jaho said:

Here is cheaper place to get heatsink:
http://www.cpfmarketplace.com/mp/showthread.php?p=2166815#post2166815

Click to expand...

After adding on $7 for shipping its not so much cheaper. I ordered a heatsink and P7 emitter from fenix store and had it in three days. I live in a neighboring state, but shipping times will still be faster then ordering from overseas. To some people it may be worth spending a little more. Yet another person to get a P7 heatsink from would be from F22A. Personally, I like his design best. It's similar to the Electrolumens moatsink.