I have been using a Kowalski 1250 rechargable Light for the past couple of years and I was more than happy with the light output from it with a 50W halogen BRL and a sizeable 3 inch reflector. The downside is, that with a hand held torch, battery size is a consideration, and even with the small 3 amp nicad in this torch it's still a bit heavy. With a 50W bulb burntime becomes quite limited, at 12V you are burning ~ 4.2 amps/hr this means only 45 minutes or so under optimal conditions.
I decided that I wanted 50W output at least but wanted enough battery capacity to get at least 2 dives on a charge with a little spare. The only way to manage the requisite battery pack is to go for a canister and umbilical arangement, that way the weight of the battery is kept on your waist and you only have a lightweight lighthead to hold.
Like most, I'm sure, I felt the prices for umbilical torches were prohibitive, at least from the divekit manufacturers. I searched the web and came across info about the 'Divelight Companion' by Steve Lindblom from Airspeed Press. Without delay I ordered a copy which I received, from the US, in a week or so. This really is an invaluable text for the DIY dive light builder and I would highly recommend it.