The trend in colors is white cabinets. If you really like the dark, I would suggest white cabinets with a dark island, so you will get some of the dark. If your kitchen is large enough you could add another dark element--such as a dark mantled stove area.

Mixing countertops is perfectly acceptable. Just keep in mind the size of the space you are working with. The more broken in colors, the smaller it will appear. That is not a problem is you have a space large enough but if your kitchen is very small, it will appear smaller.

Wood floors are really popular in kitchens. If you really like tile, I would express that on the backsplash. If you decide to use tile on the floor, I would go with something that looked more like stone with a very small grout line. If you have a large space, a diagonal pattern might look nice. If you have a small space, and offset grout line would look nice.

White easier to sell and more practical (cant see finger prints, it's like with white iPhone). Also matches w everything.

White would be the easiest to sell.