Well, the brightest and longest-throwing single LEDs that I know of ar Malkoff's modified maglite's
here, if you can afford them that would probably be your best option given your criteria. Since it's custom heatsinked, the LED is free to run at maximum drive, regulated. If you want a good drop-in module for your maglites, the Terralux Seoul SSC available at
Battery Junction is the brightest drop-in bulb for a maglite available -- should produce about 50% more lumens than the MagLED, but with no dropoff at all (MagLED drops to a fraction of original to keep from overheating itself -- since Seoul module is more efficient, it doesn't get as hot to produce the same light) The drop in module won't be at full capacity though because of heat constraints, like the Malkoff.
If you really want a lot of lumens, there are multi-emitter modded maglites, however, I personally like the simple elegance of single emitters -- for one thing, with big reflectors, you get the advantage of a tightly collimated beam for throw, which isn't as possible with tons of tiny reflectors, which are better for making a "wall of light".