The Janna is from the Classic range, a traditional pocket sprung mattress topped with a lyaer of luxury fillings.
The Kassia is an orthopaedic mattress. The term 'orthopaedic' generally just means an extra firm bed; it is not based on any medical or other common standard, nor does it mean the bed has been professionally assessed or recommended. It is a term loosely used by manufacturers to refer to extra firm models in their range. Firmness is not determined by price, although comfort, luxury and durability and added features such as adjustability come with higher price tags.
The Casablanca will feel similar to the Janna, but has pure new wool, silk and cashmere in the fillings.