Garry Edwards , Nov 14, 2005; 07:38 a.m.
This is a very common problem. Very little raw power is needed for headshots and the ability to adjust the output of the lighting is IMO far more important than the amount of maximum power. I find, typically, with a medium (4'x3') softbox set very close, and the power dialled down to the minimum of 37J, I get around f13 @100 ISO.
The answer is to use neutral density gels, either over the lamp itself or over the softbox.
Coincidentally, If you go down a few posts to 'Monthly Lighting Project' you'll find it covered there.