Hi Paul, I have a few REW in room measurements from last fall. They are a bit messy with room modes and such but I could share if you send me an email address. I probably live 10 minutes from you, I'm in Chandler.
I haven't studied your case but I have Cornwall IV's and ended up using a Heresy IV for the center. It's excellent. I referenced the tweeter / midrange descriptions on the Klipsch website spec sheet and was surprised to see the Cornwall IV and Heresy IV use the same tweeter / midrange drivers. I don't think you're going to be as lucky though but hopefully this post will help a future person searching this topic.
Cornwall IV & Heresy IV Tweeter & Midrange:
K-107-TI 1” (2.54cm) Titanium diaphragm compression driver
K-702 1.75” (4.45cm) polyimide diaphragm compression driver