CAAD13?

Depending on what spec Caad13 you're looking at, the Bowman Palace 3 disc is available with a full Ultegra groupset and decent finishing kit including hand built Noble wheels for £2.5k. I can highly recommend, brilliant handling and responsiveness, along with all day long comfort. ​

I've got both a CAAD 12 (rim brake) and a CAAD 13 (disc brake)

The 13 is definitely a more comfortable bike but I would say that the 12 feels stiffer to me and more responsive to my efforts, that could also be down to the fact that it is lighter due in part to the rim brakes. 
I've done 200+km rides on the 12 so it's certainly not uncomfortable but the 13 feels like you're riding a carbon bike whilst the 12 is unmistakeably an alloy one. 

My 13 is currently my winter bike with it's full length mudguards and the disc brakes whilst the 12 is my summer bike. 

To be honest you can't go wrong with either of them although the stock builds of the 13 are pretty insipid with poor wheels, cheap finishing kit and obvious scrimping on groupset parts. I bought a frameset and built it up myself and I've got a bike I'm very happy with. 

It's a nice bike to ride. I've made quite a few changes to the stock bike, but the frame itself if comfortable and nippy. I bought it to train on mostly but I've raced on it just fine at the start of last year and didn't feel like I was disdvantaged doing so. I've never ridden a caad12 but from what other people have said to me its quite a firm ride. Think the caad13 isn't quite as aggresive positionally either.

The only real issue I've had was a constant clicking which turned out to be the seatpost but that is sorted as long as it is well torqued up. It took me ages to get one pre-pandemic so I feel that might be an issue now. The only thing I dont really get are the quick release through axles which mean the fork is designed around that. Never in that much of a rush to get the wheel on/off.

https://road.cc/content/review/cannondale-caad13-disc-105-2020-269731

CAAD13 was Road.cc's road bike of the year last year wasn't it? If you google it you'll see plenty of other reviews from bikeradar, Cycling Weekly etc however always good to have a review from real world owners. I'd suggest asking in the CAAD groups on Facebook for lots of opinion.

Full disclosure I work for Cannondale but CAAD13 in my view (having ridden one extensively) will give you a very similar ride experience to the SuperSix EVO, at a slightly heavier weight but also with a bit more practicality (mudguard eyes and added durability in case of falling over at the cake/coffee stop for example).

What are you riding currently and what are you hoping the new bike will offer you that your current one doesn't?

And yes it's a very upgradable platform, you can make a very high spec' CAAD in the future if that's your plan.

Hope this helps.