what to look for in a softbox purchase... are Calumet / illuma good buys?

I hasn't been mentioned (yet...), but you can use Neutral Density (ND) filters on your lenses to cut down on the light your Camera sees!

They act just like sunglasses and come in densities ranging from ND 2 (absorbs 1 f-stop of light) to ND 16 (absorbs 4 f-stops of light) and even NDx400 (absorbs 9 f-stops of light).

You don't have to have an ND filter density X / lens size X either as
you can use a larger size ND filter with an adapter/lens size,
and they can be 'stacked' to add up to the density you need.

This article mentions all the many other great uses for ND filters, except the one you need!
http://www.cambridgeincolour.com/tutorials/neutral-density-filters.htm

Its almost an 'off-label-use (sic)' of ND filters because few people use them this way?
(With more modern lights, the need isn't there anymore.)

Michael Rose