Ambient? That's the light in your room. If you want it closer to daylight, replace incandescent bulbs with daylight-balanced CFLs. You can go cheap, or find a good lighting shop and buy some full spectrum daylight with a high CRI (expensive).
Frankly, if you keep the room not too bright, then for looking at your monitor it doesn't make all that much difference (some yeah, before people jump all over me. I do have good quality CFLs too :-). If you really want to do it right, aside from the high CRI bulbs make sure you paint the room netural gray, and don't have anything colored in the room. In all honesty, the most important thing is to have a neutral desktop when you're editing; my screen background is set to a somewhat darker than middle gray.
Where the color temp of the ambient comes in to play is when you're printing. And for that you ideally want a viewing booth, but if you don't want to spend (anywhere near!) that much, get a portable Ott-Lite
Amazon.com: Ott-Lite Truecolor Portable Lamp: Kitchen & Dining and use that for looking at your prints.