If Pat doesn't mind.. (it's all Presonus relevant)
It's often said the price difference between AVB and Dante is because of the extortionate licensing cost of Dante. The reality is that Dante is provided on a chip by Audinate which manufactures build into their equipment.
The chip handles everything. There are several versions of it, the difference being the number of channels it supports.
AVB is handled by the hardware directly, relying on the network interface with AVB ethernet extensions to work.
The only way to add Dante to the CS18 would be with an option card that includes a Dante chip, but the CS18 doesn't support option cards.
You are right Jeff, it would have been totally logical for the CS18 to have the same expansion slot that the SL and RM units have.... but since when has Presonus ever done anything logical? Their individual products are great, I have several, but there's someone high up in the product development chain that seems to be running around like a headless chicken.
Audinate has a
whole series of videos about Dante (obviously) and digital audio networking in general which I recommend, especially the infocomm RU credit courses. You don't have to register for the course, or apply for the credit, but run through it and you'll learn a lot from it.