I currently have a 3 cell M*g Krypton bulb driven by two fresh Battery Staion 123s in one. You'd think it would
and a 2 cell did. The 3 cell is frosted, so throw isn't all there but it's pretty bright.
edit> I just put an un-frosted 3.6V K3 in the light and the beam doesn't suffer TOO much. It's considerably brighter too... <edit
In others I have SMJLEDs, One has an Everled, One has a Craftsman LUX "bulb" driven by a 17500 Li-Ion.... and so forth.
I don't know beans about two stage mods.