Seems like you can do well with a few cheap strobes like the Vivitar 285 HV or similar and some DIY light modifiers. For ideas on light modifiers browse through http://strobist.blogspot.com. The Vivtars can be cut down to 1/16th power (maybe 1/32nd) and if that's not enough, you can always gel them down another stop or two with some Rosco cinegel ND material. The Vivtar 285's are inexpensive, and the ND gel material is dirt cheap at about $6 US for a 20 x 24 inch sheet. Add a couple of cheap optical slaves and you're good to go.