Here is what Classe states:
All amplifiers except the CA/CT-5300 have a virtually linear doubling of output between 8 ohms and 4 ohms but since it can be a misleading figure, we do not supply details of their performance at 2 ohms.
This by no means implies that our amplifiers cannot operate at 2 ohms, which they obviously can. Impedance varies with frequency and most high quality speakers have the capacity dip to 2 ohms. Since our amplifiers are specifically designed to drive the world’s best speakers, they will have no problem driving a 2 ohm load.
Nevertheless, driving 2 ohms in the real world requires an enormous amount of power, which is sometimes technically unavailable from the AC mains power outlet. This means that these types of specifications are vulnerable to external conditions, and can therefore be misleading. Clearly, we do not want our customers to make decisions based on potentially misleading information.