Whether using the MX-600 that has clear glass or the MX-601 that has diffused glass (we use both), from single or dual bulbs from 5W to 20W each, you will find great fill-light at 15-feet+, or great light from total darkness up to 15-feet using twin 20W bulbs. The lamps are instant-on halogens with individual switches for independent use (and off-center fill, and unbalanced fill for effect) that we've also used with different wattage bulbs at the same time (great for applying less light on one side of the scene and more light on the other).
Some may criticize the X645 battery pack's design because it is prone to slip off its clip, but we just turn the clip upside down and it is so strong that it stays put; we've also talked to Bescor with a design change they are considering that will make quite a change for the X645. Besides, their other batteries are either shouldered or are belts with at least three of the major connector types available.
Do we work for Bescor? Nope, but we searched for reliability, variability, variety, weight (we use steady cam rigs) and serviceablilty for video lights on our Sony Z1's which all led us to Bescor's selection of lighting.