Eneloops are great batteries and can be had in combo packs with both AA and AAA and a charger that works with both. As long as you are sticking with Eneloops their included charger works just fine. If you plan to acquire more flashlights over time or look towards more exotic Lithium Ion Rechargable batteries there are smart chargers from folks like the Nitecore i4 Intellicharger that will charge a greater variety of batteries (including Eneloops) with a greater variety of battery chemistries.
Eneloops work great in an SC52 but the 500lm burst mode requires LiOn 14500 type batteries (I use standard blue non protected Ultrafire 1200ma cells but you will want to read up on the different kinds of LiON cells and their dangers and merits before you go there). Nothing wrong with the stock 280lm and the long battery life of the Eneloops though.
As to a headlamp, have you considered a single AA headlamp like the Zebralight H502 so you have battery interchangeability with the SC52?. Depending on your use you might even be happy with an H502 instead of the SC52 (although the H502 is pure flood, only suitable for short distance)
My favorite AAA headlamp is the Petzl Zipka for its ultra compact design and decent 3xAAA output.
Hope this helps