I would be more concerned with how those two cabinet colours work with your wall colour and concrete palate. I think one will be more favourable than the other if you can put samples together. Also keep in mind what lighting you'll be using. Since if you have cooler colours then 'cool white' 4000K lighting will look best, likewise if you have the warm Alabaster colour then 'warm white' 3000K would be best.

It happens because houzz recycles very old posts into the daily feed. It's a totally useless feature of the site and serves only to cover up the fact they are lacking in daily content additions.

I have done exactly that. 600x600 on the entire top floor including the out side area and the bathroom. The outside stairs and the front porch are exposed to the weather so I have a more textured non slip version of the same tile. Very happy with the my choice.

Go for option C, possibly with a dark timber for contrast and drama. If it is slightly different it will look slightly off and annoy you forever. However I would be asking the question "why it is not available for stairs?". Stair treads get heavy use so you need a durable timber. If there is a question over the durability of Whian Whian Blackbutt for stair treads then maybe you should reconsider it for the rest of your floor? Best of luck, Dr Retro of Dr Retro House Calls