this one is called class T.
See www.tripath.com for further informatin, the tripath chip set is the engine of the Bel Canto amp.
I believe the digital amp will direct the future of the amp design, simply due to the decrease in weight, heat and size with the efficency >90%. This is especially true for nowadays multchannel home theater environment.
Although the digital amp is not at its prime time at this moment, it does eliminate the cross over distortion in the class A/B amp design and this make it approach class A SET amp design. Of cause, all this assume the amp operates with min jitter, good output filter, excellent dithers and so on. In addition, digital amp also provide basis for the full end to end digital chain music reproduction. In theory the chip set can be designed to take the digital output from CD player and drive the speaker directly. Digital signal processing can also be used to do EQ on amplitude and phase. This will natually lead to digital crossover and multi-amp configuration. I speculate Klipsch's purchase of Aragon will have something to do with this design in the future.