You have a large room. That may not be a factor in choosing the mains as much as the size of the listening area. If the extra $900 doesn't break the bank, I'd go with the 80s if for no other reason than to avoid the "what if" factor.
Where the size of the room WILL come into play is your choice of subwoofers. The Ultra is a good sub, but so are the Axiom EP500s and EP600s. The Ultra will reach a bit lower and play a bit louder below approximately 23 Hz. But above that point, where something like 95% of bass information can be found, the Axioms will have the advantage in smoothness of frequency response, and volume. In short, they will sound a bit "better" than the Ultra.
I own an EP500, so I plead guilty to being biased, and won't be offended in the least if you go for the Ultra. It is a good sub. However, in a space as large as yours, whether you go with SVS, or Axiom, or HSU, or Velodyne, etc., I suspect you are going to want to go with two subs.
One of the guys here (Jakeman), runs Axioms for the above 23Hz (or so) material, and runs an Ultra for the stuff below that. You might investigate the possibility of doing the same.
You could certainly "get by" with 3 QS8s OR 4 QS8s. But, again, if it wouldn't break the budget, with a room that large, and to avoid the "what if" factor, I'd go with 4 of them.
Welcome to the forum.
