First, marble tables of any kind are bulky and heavy. Second, they have to be well looked after, as the marble can crack and stain. To avoid stains, keep the table cleared and clean at all times, covering it with a tablecloth or placemats when red wine and foods that can damage marble are on the menu.
It is likely that you will take the new items with you and so it wont be a wasted spend and could end up selling your home if it helps to make the room appeal to buyers. If you dont take them with you and the buyers like the space, you could offer to sell them - this is particularly handy for first-time buyers.
To visualize how a bigger piece of furniture will look, take the time to block out the length and width on the floor, and also the height of the table. I usually stand on my tape corners with a tape measure, then try to fill in that space with furniture of a similar size, and take a step back to see how it’ll feel. It also helps to have a friend stand there with the tape measure while you have a look.
If you’re tight on space, consider options like leaves that allow the table to extend. These let you customize the table for different entertainment needs and party sizes.