If you were still looking for some warmth and a little variation look at Dulux Natural White or Casper White Quarter. Both work well with Vivid White, so will still work with your trims and kitchen cabinets, however will provide a slight difference between your walls and trim work. In saying that there's no problem in using Dulux Vivid White for both walls and trims.

Given the wall behind that sofa is going (did I read that right?), I'd not replace with anything other than some more photos on the wall perhaps....just for the interim. Oh gosh- I'm sorry about the rug. I'd be looking to pull a colour from the adjoining dining room- the lovely linen/neutral colour from the chairs would look good, a natural sisal, woven grass-type (West Elm has some on sale). Could the new Ikea rug go under the dining table?, to take colour pallet across the dining room. In terms of a coffee table- round or oval, glass, finely detailed legs. Something that almost disappears. Add a couple of linen/neutral cushion to the grey sofas, a neutral throw. This would really lighten the whole look up.

I think you really can't go wrong with Natural White, but I would try continuing the Grey Pebble and just being mindful of introducing surfaces that will reflect the light such as a big mirror, a large light coloured print and some light timber furniture. And of course it's a great opportunity to introduce some amazing lighting!

try snowy mountain quarter........i would suspect it would go with both warm and cool tones..i have in my house after having had both of the other colours that you have mentioned, and the SMQ is just so much more versatile....there are a few discussions about it on this site if you want to do a search