FWIW, I agree with Michael and Nick - if you can, bite the bullet and buy a decent monolight to begin with. While these hot light sets are attratively priced, they are extremely limiting. Even if using 250W bulbs, most people will be uncomfortable with that level of light close to them, and they'll become beady-eyed grumps. Even then, you may have to compromise by using faster film than you'd like.
One not-so-subtle difference with using strobes with softboxes and the like is in the subject's eyes. The lower light level during setup allows the subject's pupils to open up, making the resulting portrait seem more "inviting" and friendly. Small pupils resulting from hot lights give the opposite impression of the final images.
Look at the different brands of monolights, and pick one that offers future expansion, and that has adapters for the softboxes you like. Then, build your sighting system over time. Most of the better monolight systems will allow some control over the unit's output. For example, the WhiteLightning strobes I use provide continuous adjustment, which is quite handy. Others offer stepped output adjustments.