my recommendation is as follows:
get 2 3AA>1D adapters (just basic ones, nothing fancy, spend a few dollars here)... if you want to get fancy beef up the contact points in the battery carrier with some solder... do the switch mod or part of it to keep things simple, or just don't worry about it for now, and try it later to see the difference...
get 6 NIMH AAs, head on down to radio-shack, and maybe swing by a few hardware stores, pick up a bunch of bulbs to play with. 6V bulbs are usually about right, anything rated for 5-6 cells is worth a try, some bulbs rated for 4 cell alkaline setups will actually survive 6 rested NIMHs pretty well. The king of simple low-power PR bulbs on this setup is a mag 5 cell xenon, which might require letting the cells rest a bit to avoid instaflash, but it's a rocking bright bulb that throws like crazy in a smooth reflector...
The reason I recommend this, is it gives you a chance to play. You get to experiment with different bulbs and see what performs and what doesn't, what blows up and what survives... Then when you want MORE light, mod the switch, buy an aluminum reflector and a glass lens and go with the ROP setup, or get a KIU socket and play with bi-pin halogens.