What's important is a great set of objective ears, years of experience and a great room with a true sound. Look at this way: If the equipment in a studio is a high performance car, and the mastering engineer is the driver, putting the car on ice and trying to achieve a good lap time is like trying to master music in a bad room, all the equipment in the world wont help you connect with the music and let you hear what's really happening. The room is the environment in which the mix performs to its potential, as the road is to the car. It's hugely important.