Posted by Justin :
Not to nitpick, but 4 400w/s monolights will be equivalent to 4 heads on a 1600w/s pack, not a 1200w/s pack.

Also, having used both the strobist hotshoe flash technique, and then upgrading to studio lights. I would take the studio lights every time. They are more powerful, accept a great deal more modification to their light, and generally help you learn about flash photography in a controlled way. I still use Nikon speedlights, but when I can, I bring out studio strobes and battery packs.