I have done a master bath with a similar color scheme, and believe it or not we used a tumbled limestone on the floor. The gray was soft and the tumbled non-shiny texture made the polished
marble countertop and tub surround look that much more shiny and rich. I can't remember the price point of the limestone though...

Thanks a ton!

What I did was take marble with me to a couple of tile stores and hold it up (in the light) to all the porcelain tiles until I found the perfect compliment. Our bathroom is kind of old meets new with a grey marble so I used 12x24 grey porcelain tiles on the floor and walls. Tile had a wavy stranded look with hints of white and tans so it matched the variations in the tiles.