D cells do make for a great light when teamed with decent LEDs. A 50 lumen LED upgrade to a 2-D maglite makes for a pretty decent light. Just a slight twist to focus the maglight reflector and those 50 lumen have a very good throw. Same with the 140 lumen LED I put in my 3-D maglite, just brighter and even more throw. I cannot imagine 800 lumen.