There are 4 models of Oracle Database Appliance with the new ODA X6 which is for the moment the latest ODA hardware version. One is similar to the previous X5-2 one, and 3 smaller ones known as ODA Lite. They are 1 year old already, here is a small recap of the differences and links to more detail.
System
The ODA X6 are composed with Oracle Server X6-2: