Change the island top. beautiful walnut or a piece of granite. leave the large perimeter counter / it will work w something else at the island and youll save money. if funds are no issue then many granites would work for total counter replacement.

How many square feet? 50-60 maybe? This is a $6,000 to $9,000 fix if you do quartz. Higher priced exotic granites/quartzites will be more. The black looks nice...gives the room contrast. A white marble look here will look bland without a tile backsplash to add texture. This space calls for a short-mini splash...no tile work....and a darker top or a top with movement.

Short splashes are becoming popular. Google it.

I think this is abig expense and IMO quartz would be a down grade form the real stone it appears to be But that said many real stones could work in thta space but we need more info and much better pics of the cabinet color. For me the cabinets are dated so to install new counters on dated cabinets really never makes sense to me . Blk and whyt is classic and suits the cabinets you have .

Remove the granite riser, enclose the fridge, and tile the wall. Much more impact.

If you are not a big fan of black and white, what are you a big fan of? You need inspiration images. And you need to think about your backsplash as well. Will you go with the 4” again? Your outlet placement makes that the likeliest choice.

If you are keeping your white cabinets, Google images of white kitchens and see what grabs your eye.

Need some color to punch it up. You have wall space for some colorful artwork.

I like what you have, I wouldn't change it.