worth the jump to Cornwall IV's from Forte IV's?

Yes!  I have had several editions of both over the years, and the Cornwall always sounds better in just about every way.

Having owned Khorns, Scalas, Herseys, CWalls, Fortes, and being a Heritage lover for many moons, in a simple word...YES....

OP,  I made the move from Forte IIIs to Cornwall IVs.  It is a definite upgrade, yet the Fortes are great in their own right.  Gutenberg described the CWIVs as a Forte on steroids.  I think that's accurate. 

CWs give you very accurate bass. I do, however, use them with subwoofers, which is not necessary--just a great next step to take the system to a higher level. 

They do great with tubes and surprisingly good solid state. They reproduce what you feed them.

The recommendations above about Volti are good too.  They just get super pricey when you option in the real furnishes and features. 

thanks very much all for the feedback

after much consideration including feedback from a dealer contact who sells Cornwalls I've decided against the CW's and will be seeking to audition the Paradigm Founder 120h's, Personna 3F's , and possibly acquire used Signature S8s

Wow,,,different as chalk and cheese.