"The dark Tan Brown granite on the perimeter perfectly ties in with the cabinets and warm tones of the island stone, without being too busy. There's no compelling reason to spend 8K to change it."
x2. Simple backsplash change is what is warranted here, not a countertop re-do.
IMO what needs re-doing more than the backsplash is the color of island. It looks like a dark navy on my monitor, and it just doesn't go with anything else. Even if it's black, it just sticks out like a sore thumb. Paint it something that better coordinates with everything else.
Q
