If you don’t want to spend too much money and don’t mind much the XP-L2 led, I think the SP32A v2.0 (review by gchart) would be a good option, as it last a bit over 3 hours at 500lm and also has a ramping mode, so you can change the brightness if high is too high and medium too low (I’m not sure if the efficiency in ramping mode is the same as in normal mode at the same output). I have the SP31 (some intermediate model with XP-L2 led but v2 UI), the efficiency is quite good and should be about the same as the SP32Av2.0 but the latter should tailstand much better.