I probably would steer away from black if you want to keep the country theme

Concrete bench tops and decorative concrete pieces are a good idea if you like the solid look. I certainly would not recommend asking a general concreter about a concrete bench for your kitchen. Normally the bad rap that concrete bench tops get are when they are manufactured like a driveway or footpath. Kitchen bench tops require different characteristics. They should be constructed dense (to help prevent staining), flexible (to prevent cracking), lightweight (so can be manufactured off-site). With the materials that are available now, concrete can have all these characteristics. Sealing is another topic for the professionals. There are three different methods of sealing concrete. Penetrating, Topical, or Reactive. Sometimes all three are used to seal a concrete kitchen bench. This is because the way a kitchen bench is used is different to a floor. You are not only trying to prevent staining, you are trying to prevent etching that could occur with acidic foods. There are companies around that specialise in concrete bench tops for kitchens. Try them you may be surprised at the options available for "concrete" bench tops.

I'm not 100% sure what you're asking, but if you're looking for suggestions whether to make the lower cabinets grey and the upper cabinets white or vice versa, then I would be tempted to make the lower cabinets grey. I think this would help to make the ceiling feel higher and the overall space larger and brighter. But, it may depend upon what style you're going for, whether you have an island benchtop and, if so, what material/colour will be on the rear/exposed side of the island benchtop, the amount of natural lighting, etc. You can easily search through Houzz photos by room, size, colour, materials, etc. Here are a few examples I found from a quick search which may help:

Hi! Number one is to make a space that makes YOU happy and works for YOUR family. Second - having sink or stove on the island means it is front and centre all the time, if cleanliness is something that worries you, then perhaps this isnt the best option. Third - I have seen bench top materials that mean a stove top can be seamlessly integrated underneath, this would solve the presentation issue as it would look like regular part of the bench and be easier to clean than a regular stove top Fourth - What is the layout of your space? Is through the kitchen used as a walk way for little ones? I always recommend that the stove be where the least amount of foot traffic occurs, to the side and out of the way! Good luck