Changing light in my office room. I have some of my client complain?

about the light. I tried buying yesterday the 40 watts from Home depot and it was day light. But it turned out to be even worst than the one I currently have. I noticed that there are the following: Day light, Neutral, cool white, Natural, and soft white. Which one would be the best to get the room to be more bright? Is there a different brand I can buy from somewhere else to make the light in the room better? Lastly, is 40 watts the highest?