There're 2 choices of the lights, one is 4 inch , one is 6inch.
If there is a room around 100sf - 150sf , you will need 4inch x 4.
If you prefer brighter, you may select 6inch x 4 ( really bright as it suitable for a family gather at living room).
if you are using 6inch light, you may choose to only switch on 2 lights at one time to save electric bill.
Note: The estimation above are for 9ft wall


4000K(a.k.a cool white) is a bit yellowish, but it depends on your wall color and ceiling color.
The more yellowish your wall, the more yellowish the light is.
If your wall is white, you wont feel too much difference with white color.

I don't suggest you take 6000K as the light is too bright, everything will become grey+blue color instead of showing the actual item color. For example, your wall is white color, but the light will cause it looks like kinda grey+blue, the color became not really natural.

This post has been edited by Kopilowyat: Jun 8 2015, 03:49 PM

More than enough
It doesn't look like orange color as 2700K (Warm White)

A big no no for 6000K, especially rooms. I only have my toilet lights 6000K because my tiles are brownish yellow, I don't want 4000K light make my toilet become even yellowish.

I saw a lot of people bought 6000K LED lights from houses lighting.
I wonder how they tahan?