I would go with a darker countertop since you already have white cabinetry and would like a white subway tile backsplash. This will bring some contrast to the space--which will also enhance that vintage style.
I love the suggestion of Soapstone countertops. Here are some other granite options for you: Silver Pearl, Steel Gray, Black Forrest, Black Pearl, and Absolute Black. The Black Pearl and Absolute Black in a honed, leathered, or antiqued finish also look lovely as well.
If you want to do a subway tile backsplash, I would not worry about the 4" granite backsplash in the back. Doing all tile is a much better look.
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backsplash dilemma
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