When you look at strobes, always look at the amount that the power can be reduced to and whether it can be continously varied or has to be reduced by steps. Most of the good current strobes will adjust continuously from full power down to 1/16 or 1/32 power. This is 4 to 5 stops, depending on how you look at it. Many of the cheaper ones and most of the older ones only had three settings, full, 1/2 and 1/4 power, 2 stops. The greater the adjustment range, the better off you are. There are many times that you will find that you have too much power. If you can't reduce the power level, you have to move the lights back or increase your f-stop (or use neutral density gels) which may affect the quality of light or depth of field. One of the big advantages of the new digital cameras is the ability to change ISO speed ratings with little loss of image quality. I usually range from ISO 100 to 400 and that gives me two additional stops. It is impossible to predict the amount of light that you will need until you can actually measure the amount of light delivered to your subject. I would generally suggest systems with around 300 to 400 true watt-seconds per head with as much turndown as possible. For me, the Alien Bee 800's with the remote control will be the ideal system. I can't afford it yet, but there is no point in spending money on something else.
I hope that this is useful to you.
Bill
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