Do you care whether other people's powder rooms match their kitchen? If a room has a door it can have completely different colors and style. If the fireplace and bar are not right next to the kitchen there really isn't a problem. In some very open floor plans people choose to put tile next to hardwood to distinguish an area.

Below is a kitchen with gray, white and dark brown features. IMO, nothing clashes. I'm not saying the style is perfect. I am saying style is personal, and if you like something you should go for it. If you are unsure of the white quartz go look at more samples with some brown flecks in them. Compare the different samples, and, if you can, try to get a sample or two to take home. If nothing else take a photo of each sample and compare them while standing in the space you are redoing.

what is "amused white finish" ? and post pictures of what you're referring too. have no idea what "brownish stones" mean.

you don't need to match your kitchens to your bathroom. if the living room is open to the kitchen, it's nice if they compliment each other.

Really what is an “amused” finish I am sure it is a typo but can’t for the life of me figure what it should be. As above bathrooms need not match kitchens. I like a powder room to maybe have some connection to the main living area but other bathrooms to me should be more connected to the bedrooms they serve.

Probably “cerused”. Which is a high dollar upgrade that is not suited to very many design styles.