Which speakers will fill 5,000 cubic ft coherently

The accuton drivers are not well known for playing loud/dynamically. So it is not surprising that a two way with these drivers might struggle in a large space. To me I don't think you need to go overkill - most equivalent price range three or four ways would make you much happier, IMHO.

I am not sure you need to go overkill but if you want beauty and assurance that you will be able to fill the space then Dynaudio Temptations, Wilson Alexandrias, Evolution MM3's would all do it without a single doubt in my mind.

You need to better specify what volume level you desire. You should also state what amp(s) you would be using.

80-90 db, Atma-Sphere MA 2.2 OTLs, 220 WPC.

Budget: $15K (new or used)

My overall space is 45' x 20' x 18' (tall). My Zu Definition 2s sit at one end and fill the entire space with music with ease.