Most indoor lights have a lighting temperature of around 3000 Kelvin. The light appears somewhat yellowish. However, daylight is anywhere from 5000-6000 Kelvin which appears more blueish and whitish when compared to regular indoor lights. I just switched to the 5000K bulbs and have had some great results. I feel more positive hanging around a brighter room versus the more yellowish room. The light coming from the outside seems to mix better with the daylight bulbs. If you go to Home Depot, you will only be able to buy 23 Watt 5000k bulbs, but going on Amazon you can find bulbs all the way up to 150 watts. This one should be about equivalent to a 150 watt bulb and two of these should give you enough lighting for a room. http://www.amazon.com/Compact-Fluor...J2/ref=sr_1_48?ie=UTF8&qid=1288963019&sr=8-48 For any room you trade from and have to hang around for hours in a day, then I think its best to have at least two lamps with the biggest daylight bulbs they can hold so you can be exposed to bright light rather then the regular "trading cave". Good lighting is relatively cheap and produces great results.
For myself, I have two windows, one lamp and one overhead light. I always leave the 60w lamp on and adjust the blinds to the interior of the room taking into account the natural light so the room is consistently semi dark (for me, this is a comfortable level to read near my monitor and using the light of my monitor). I think lighting is important for emotions and "dark"works for me.