the speedtron pack and 2 lights would work well
2400 ws is a ton of light. soft boxes will dim the light a little bit, but still ...
if you have your heart set on the speedtrons,
get a third light head and tons of honeycomb grids so you can bleed off more light
i have worked with speedtrons in the past, nice lights, but i am partial to monoblock lights.
they are self contained units ... you need less light on 1 head, you just dial it down and the other light/s
stay the same.
have fun reading through the opinion pages!
john