I think you can hit your target with a BB500 based sandwich and a Luxeon 3 emitter on top. I just built one by hand and that sucker is plenty bright. With Luxeons, light output scales more or less linearly with current, so even assuming conservative specs of 65 lumens at full power (700mA), at 500mA I'm getting somewhere in the region of 45 lumens at the LED itself. Minus losses for the reflectors and optics, 20-25%, that's around 35 lumens.
The BB500 is very punishing to alkalines though, we're looking at a 1 amp current drain from the alkalines, and the only way I've managed to get more than 90 minutes from it is by using NiMH batteries. But the whole point of AA lights is to use cheap batteries.. /ubbthreads/images/graemlins/smile.gif
I built my sandwich by hand, but dat2zip's sandwich shoppe offers prebuilt, turn key packages. You unscrew the MiniMag on both ends, remove reflector and guts (just pry off a small plastic tab and everything drops out), drop the sandwich in, drop the reflector in and you're in business. Cost is an issue though, the BB500+Lux3 kits are $60 and you will definitely want a Kroll clickie switch, make that $65 before shipping. Streamlights go for ~$30, they're definitely making good use of their better process technology and sheer volume to cut costs.