Pay attention to good quality movies and commercials. You'll find they often use a similar approach. If you have a good rim light to separate the subject from the background and provide some shape and depth, providing a lot of key light isn't always needed. Sometimes it's better to keep the subject a little bit in the shadows to add a sense of mystery or interest. With the rim light providing the shape and contrast, the fill only needs to be strong enough to show major details, not necessarily with extreme brightness. It's kind of like the idea that you can sometimes get more attention with a whisper rather than by shouting. The rim light says, "Hey, look over here." Once you've got the viewers attention, the key light only has to whisper.
The rim light came from a Canon 420EX Speedlite, positioned camera left and just over the shoulder of the subject. The key light came from a Yongnuo 580EX with a 60cm x 60cm soft box placed to the camera-right of the subject. Both were triggered by a Yongnuo ST-E2 wireless trigger. The camera was a Canon T2i with a standard kit lens. I could have used my fixed focal length 50mm f/1.4, but this shot was hand held and I wanted the extra insurance of image stabilization to maximize quality. As you can see, sharpness isn't an issue, even with this rather inexpensive lens.