One thing you may want to consider since it sounds like you can splurge if you want to is noise and just the return system in general. Ball returns can be very loud and clunky the pro am is very quite and just in general is a quite playing table. I was worried about playing late nights in my basement with the wife sleeping upstairs but the way the cushions and returns are set up along with the liners they play without much noise and are butter smooth. The three piece slate is actually thicker than 1 inch 1 piece don't know if that makes any difference in the noise dept but everything is just smooth and low decibels when it comes to play. I hate any metal on tables that can ding your cues. Diamond solved this problem. Just food for thought.I don't know dimensions but it's plenty big. Room for the table is not an issue. I put markers down for the size of a table and eyeballed it running N-S and E-W in the room, allowing room for the cue to extend to the walls or obstacles all around. The issue is having room to have a sitting area, including watching tv, even when not playing pool. It's possible that I will sit in this room more than any room, might be my go-to room due to it has lots of glass to view the backyard. So, it might be that every square foot of room is crucial. I will know more when the owner gets their furniture out.
EDIT: The game room in my current house is 20x20 and the one in the new house is larger. Probably 20x30 or more. BUT... there is a bar that juts out into the room at one end.