Spark has released their AA version of the sd series headlamp. It seems the runtimes are slightly less than the 18650 version and the max lumen is 300. Also the body is slightly shorter and fatter.Here are some comparisons from the website:
SD52-cw
Led: CREE XML T6 cool white
5 modes
Super: 300lm/1.5hours
Max: 220lm/1.9hours
Med2: 80lm/7hours
Med1: 12lm/43hours
Low: 0.5lm/50days
* Upon data are based on testing with 2*Sanyo eneloop
* Use 14500 to get maximum output
SD6-500CW
Super mode: 500lm/1.8 hours
Max mode: 220lm/3.5 hours
Med2 mode: 80lm/12 hours
Med1 mode: 12lm/120 hours
Low mode: 0.5lm/90 days
Battery
One 18650 rechargeable Li battery or two CR123, working range from 1.6V to 6.8V