I’ll second Cereal’s suggestion. H22A’s heatsinks are really nice. If you plan on leaning towards high-power then I’d recommend sticking with the flat-top P7 heatsink – as far as I know it has the most meat and the flat top is a must for mounting MCPCBs such as the Noctigon. I have never owned his rebel-reflector heatsink, so I do not know how it compares but I assume it does not have as much meat as the P7 version since it’s deeper set. I do have both the DHS and P7 heatsinks.
Running 4 18650’s may not be the most practical solution for a single emitter on a budget. I’d say 3 cells and a spacer will make life good. You could also run 4x quality NiMH D-cells, but that’s expensive. The NiMH solution allows you to run an AMC7135 based driver with an ATtiny13A and that allows you to run one of the many cool firmwares around here, such as the STAR firmware.
If you want to stick with Li-Ion and run 3 cells with the spacer you’ll need a buck driver. The driver HKJ reviewed here may be a good option in that case, but it’s not available through IO anymore – maybe someone else can chime in on where to find them these days.
Edit:
Here are the rest of HKJ's driver reviews.
Here is TorchBoy's driver database on AQUALAB.