You might be surprised at how many photo assignments you can handle with a compact, lightweight monolight like the Impact Digital Monolight 400W/s (120VAC). It's got 400w/s of power in an easily transportable package, and light output that can be varied in 1/10 stop stages over a 4-stop range, accessible through the digital readout.  The 150W modeling light can be coupled to the flash, getting brighter or dimmer to match the actual light output, or independently set to the level you want. The monolight accepts S-type monolight reflectors and head accessories. It also has a limited Auto Dump function, firing the strobe when you reset to a different power level (so the strobe is automatically set to the correct setting for the next flash). A built-in optical slave allows the monolight to be triggered using another flash. Perfect for portraits, small still-lifes, and much more.