I hate to be the bearer of bad news, but that kit is an absolute POS. The light is a cheap piece of Chinese junk with hardly enough power to light a cantaloupe (45 watt seconds). Even for one person, you're looking at a cost of roughly $400 for one decent light, plus stand, speed-ring, and soft-box-- and that's if you get a good deal. You might be able to get away with a 160 w/s strobe for a single person, but really you'd want to aim for one with about 300 w/s of power. Ideally, you'd want two lights. Shooting 8 people is a very tall order in terms of light power. If I were shooting 8 people, I would want several strobes with power ratings of 600 w/s or higher depending on the setting in which you were shooting and the style you were going for.
For budget lights, look at the following makers:
Alien Bees/ White Lightning
SP Studio Systems
Some of my less favorite, but affordables:
You could also try looking at these brands used:
When you are looking at specs, just bear in mind that some companies inflate their watt second ratings by using 'effective watt seconds'. For example, an Alien Bees B400 is a 160 Ws unit, a Dyna-Lite UNI400JR is a 400 Ws unit when used on mains power. There's a very big difference in price between those two, however. Alien Bees are completely open and honest about this, fortunately.