Gladius is the longest throwing LED based 6V light. You could look at the Pentagon 3W lights if you dont want all the computer controlled funtions of the Gladius (strobe, low battery indicator, low level setting) and can give up a little bit of light for about 1/3 the price of a Gladius (for the handheld version Pentagon L2). They also have a version with built in secondard low level NAV LED. The Gladius uses it s 3W LED on a low setting if you want to see where you are walking without blinding yourself. Pentagon is on or off and there is a version that should be available soon with a 5mm LED mounted parallel to the main light. Right now I only know of the Xenon version of the Duolight and not the 3W LED version.
The lightest set up would be the Pentagon MS2 with integral Larue mount and push button tail cap. Its lighter than a seperate offset Larue mount and L2 but it costs more too. One of the local dealers can probably get you rig set up with just the features you want like the Larue offset mount instead fo the ARMS non offset mount, clicky instead of the tape switch, etc.