For a .25ct stone, I agree that SI clarity would be fine. A small stone doesn't show color as easily as a larger stone does, and IMHO a D color is not necessary. I would instead prefer to spend more money on the cut, so you get the sparkliest diamond possible. A great cut will make color and clarity look better than it really is. I think a G or even H color is white enough to the naked eye if you are able to spend the money you save on an ideal cut diamond.