Shelly,
Keep in mind, marble is one of those things where you may get whay you want, but are you going to want what you are going to get?
Remember, Marble is soft and can scratch and stain easily. Sealers will slow down the staining, to give you time to clean the spill up, but if left it will get through and stain. Polished marble with water on it is like ice. It can be absolutely georgeous, if done properly, but remember what you are buying. There are positives and negatives to everything.
For a more durable floor, with a similar look and feel, I personally would look to Granite. Granite is harder and more durable (that is why it is also prefered for countertops - smear some toothpaste on a marble countertop and see what happens).
Installation wise, notice the rectified edges on either polished Marble or Granite. That means that the floor needs to be dead flat or you will notice. If one tile is up or down or tipped more than another with a rectified edge you will notice. This is one reason that Marble and Granite installations are more expensive. If you're putting it in, be sure to take your time and make it level. Use white thin-set and unsanded grout with small goint lines, and aside from that as long as the structure of the floor is adequqate you will have a floor to last for years.
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J&D Tile