All you have given is a price range. And that you have a large room to fill.
This suggests you should look at larger three ways - however you will find it tough to find something as good as this monitor. It is one of the "gems" in B&W's line up - competing with speakers easily three times the cost. As you have had them for a long time then you must like the sound. You should look for larger powerful three ways with a response that competes with this Awesome on and off axis response (which has only a slight midrange "scoop") - not at all easy to achieve in the target price range you are aiming at - meaning I am sorry to say you may need to "up" the budget somewhat - your speakers, although bordering on small for such a large space, are no slouches!
This suggests you should look at larger three ways - however you will find it tough to find something as good as this monitor. It is one of the "gems" in B&W's line up - competing with speakers easily three times the cost. As you have had them for a long time then you must like the sound. You should look for larger powerful three ways with a response that competes with this Awesome on and off axis response (which has only a slight midrange "scoop") - not at all easy to achieve in the target price range you are aiming at - meaning I am sorry to say you may need to "up" the budget somewhat - your speakers, although bordering on small for such a large space, are no slouches!