Which paint colour?

Now this shouldn't be a difficult decision. I can easily help other people choose paint colours for their homes, yet when it comes to my own place I struggle to make the decision.  Maybe there's an emotional attachment, or maybe it's because I do the painting myself that I don't want to make a mistake and have to repaint the room?

Our house is painted in Taubman's 'Arizona White' - every door, window frame, skirting board and wall.  We have aluminum windows in Colorbond 'Paperbark', which is a beige colour.  I often see magazine pictures with walls painted in soft grey/beige tones accented by white timber windows and french doors.  Sigh... but that won't work for me in this house.  I'm not unhappy with the 'Arizona White' it's just that I want to lighten the walls up a bit in some of the rooms.  I bought a 1 litre pot of 'Arizona White' in half strength and one in quarter strength, and now I have walls all over the house with patches of these paints so I can see how they look in different light.  Surely it not a hard decision?

So I'm going to paint the walls in quarter strength ... I think?