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.