This may be way more than you want to know, but a lot seems to depend on what you want to spend, as well as how much you want to fuss. I have been looking at commercially available units, as well as toying with building my own.
Incandescent is still the cheapest way to go, with parts readily available. Self contained units with 'flashlight' style bulbs in separate reflectors may run up to 5 watts, and put out up to 75 lumens with a hot center spot, and a lot of scatter.
Prefocused halogens, like MR11 assemblies come in 5, 10 and 20 watt styles, with output up to 400 lumens in narrow spot (10 degree) or wide flood versions. That is an efficiency of up to 20 lumens per watt. Because of the increased juice required, the batteries are either in a water bottle, or a separate pouch, connected to the head by a wire. The very best halogens I have seen are good for maybe 25 L/w, but they were in wattages way higher than you will use on a bike.
HID lights better (maybe 25-30 L/w ?), but are very expensive (and maybe somewhat delicate).
LED is really the next generation in lighting. Obtaining comparative values is somewhat difficult as you need to carefully crawl thru spec sheets and work voltage, current and emission angle. New products have already broken the 50 L/w barrier, and prices are falling rapidly. The auto industry is on the threshold of going LED headlamps, and I think there are going to be some great new bike products on the market soon.
Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
The more the better. And the more lamps the better...in case you biff one...or 2 I use halogens but I'm cheap. I can't see spending the kind of cash that they want for HID, although the light is superior and the power consumption is lower. But I can get 75 W of power (sorry don't know the lumens) for around 2 hours using 3800 mAhr batteries that are reasonably light (6 of them) running 4 different head lamps. That's enough for me. I'm not into 24 hour events, just tootling around the woods at night or riding home from work during the winter.
I would suggest a system that lets you run at low power during climbs and full power during downhills. The more you can get on the downhill the better.
And how many furlongs per fortnight is that? The fun of mixing illumination per unit area and source intensity... Candlepower is the brilliance of the source itself. Lumens is the brightness of the illuminated object. I think you can see that the reflector you use to channel all the light output forward and into either a spot or flood, plus how far away you want the light to project will play into the answer. Plus we are mixing English & Metric units here.
One reference I found listed the conversion as one lumen equals 12.6 candlepower. I didn't do the math to verify, but assuming it is right, your 1000 candlepower light puts out about 80 lumens. In a halogen bulb equivilent, that would be around 5 to 6 watts. If my math is screwed, please, someone jump in!
I had a 5 watt light (Specialized Astro 5). It was fine for casual road riding, but not terribly impressive. I'd call that 'light to be seen' by oncoming traffic, but not a light with which to see.