Do all 10 chairs need to be at table all the time or can it be 8 chairs and 2 you bring over from somewhere else for large sit downs? DIAL UP YOUR CHAIR sizes to be proportional to table so, as to not look like child size chairs. Restoration Hardware furniture is over sized and generous proportions compared to many other retail sellers. Just any chair could be easily dwarfed by the RH table and look tiny. Here are a couple of my favorite modern chair makers KNOLL Brno flat bar chair which can be bought at auction and recovered in leather or vinyl of your choice and David Edward Furniture made for corporate, resort and colleges and available through dealers, I am showing here as a "host chair". Other "host" chair items possible of course. I just like this one.

That's an interesting dilemma. I would be inclined to go with the dark grey chairs because: - the chairs will be under the table surface most of the time, so it shouldn't be "too dark" when combined with the dark grey sofa; - the dark grey should tie in well with the sofa; and - the dark grey will provide a nicer contrast with the concrete table surface. Does the store you're purchasing from have a returns policy? If you explained your dilemma, they may allow you to take one of each colour home to see which colour works best in the space. Alternatively, can you go to the store which stocks the table, see what other chairs they have in the showroom and see if there are some light grey and dark grey variations that you can try in the store?

It sounds like you have a lot going on. I’d be looking for chairs that repeat an element you already have ie teak as mentioned but I’m having a hard time picturing them with your table. Hopefully others will be along with some inspiration pics.

Have a look at Brosa Zoe they have a 200kg capacity , they are lovely and they are on sale