Larry, thanks, i bought 1- 1 million and 1-two million spotlight by garrity corp. they say they are good for 25 minutes, but that always seems optomistic. so far i have been able to shoot whatever i want in one evening shoot using the two units. they say not to use them constantly on, but i use them in bursts from 20 seconds to a minute or so at a clip. it really is dependant on your subject distance, how much juice you will need. the barns were at roughly 60-90 feet away,and i usually shoot around f11. i would get two- 2 millions if i did it again. they are not twice as bright,but somewhat brighter.
When i first got them,i tried to make all kinds of diffusion to make the beam wider/softer, and i accomplished it,but it either was nice soft light, for closer stuff, or it knocked the thing back too far. they are actually perfect for when you get outside and do buildings or whatever. i usually hit my subject and move fairly quickly all over it,to give a softer ovrall effect,because if you pause in one region too long it has more of a spotlit effect, which can be cool also. If you want to use them for interiors, i found using a can of rustoleum- frosted glass spray paint on plexiglass, gave me a good balance of power and softer light.
Here is a link to their site. i have the S700,and S900G. I paid 28.95 for the 2mill,and 19.95 for the 1mill. I think with a little practice you could actually light interiors with these. i bought a two headed leash clip,so i can hook them to my pants beltloop to walk hands free.
http://www.garritylites.com/page79.html