I ride both, and have to say that my caygill 653 is smoother and feels more comfortable than my pinarello paris carbon. I can't say if that's due to the frame, the wheels, the tubs, saddle, position, or a combination of those things. That said, my carbon bike is a 2006 model, so outdated compared to modern carbon, which I haven't tried. It's possible that one of the modern frames like the domane, specialized roubaix, etc, that are designed to be more comfortable, will be. Personally I think that having a frame that fits correctly, followed by choice of wheels and tyres, saddle, and position, are what makes the difference between one bike and another. There are just far too many variable to be able to say that one bike is more comfortable than another! Anyone that says carbon is definitely more comfortable than steel is full of BS, and the anyone under the age of 25 that works in a bike shop is unlikely to have tried a decent steel road frame anyway!
Before dropping big money on a new bike, I'd investigate some traditional 32 spoke wheels, fitted with some wide tyres (preferably tubs or even tubeless), maybe a change of saddle and bars, along with position.
Unless you just need a decent excuse to get a new bike approved by the missus, in which case, yes of course, the new domane will increase comfort 217% over your old bike and is an absolute must in your situation!
Whatever happens, I hope you get sorted and can keep riding for many more miles yet!