I get great results from my "head shot kit" and I'm happy to report that I spent much less than some might think necessary. Below is a sample from my most recent job with the results of my separation after developing.
My point here is that I use inexpensive equipment that is just enough to get the results I want. If I shot portraits and studio jobs often I might invest in more expensive equipment to get more durability. As it is I shoot 4-6 such jobs a year, usually as part of a convention shoot, and here is the equipment I love for portability, dependability, and cost.
My lights are Impact VSD 160. They're bright enough, adjustable, and easily fired by remote triggers or on "slave" mode.
My backdrop is the Westcott X-drop kit with white, black, and chroma green backdrops. The backdrops are easily interchangeable during the shoot and the kit packs up small and light.
If I'm shooting groups against a backdrop I'll bring my much more cumbersome paper rolls with the 3-piece stand. It's heavy and much harder to set up and take down but I have it when needed.
The backdrop is lit by a Canon Speedlite to eliminate any variations.