good monitor speaker for a large room

In my limited experience the Krell Resolution 3 is the most dynamic monitor i have personally auditioned and has very good bass. (updated nodel is the Krell Res 4) That being said it is still a monitor with limited extension and you have a large room, so it will sound as such. What are you trying to accomplish? Do you have a sub?

Revel M20. You will not need a subwoofer. Very highly reviewed. You can get them used here on Agon for a fair price.
Many reviewers use this as their reference monitor.

Dynaudio special 25's (used) if you can find them.

Forgot to mention with the S25's you really want the stand4 to attach them. I would also fill the posts with sand to weigh them down.

You may want to consider the Totem Mani-2. With enough power driving it, it will fill your room with solid bass. No need for subwoofer.