GaN, Hypex & ICEpower

Don't forget Pascal by the way. They have their fans too.

I see they have a platform called UMAC...which companies use it?

Don't know much about the current buyers, but lets hope others will jump in.

ICEPower® products As the very first product using ICEPower® technology from Bang & Olufsen PowerHouse a/s, BeoLab 1 was released for sale in Autumn 1999. 300 watts of ICEPower® technology are employed for bass reproduction, providing a phenomenal listening experience.Jan 11, 2007

Infecion, it depends on your speakers. If they are reasonably efficient I would favor the Manleys. I have yet to hear a Class D amp I can warm up too other than the now defunct TACT amps which really operated in a different way. They were actually power DACs operating at 90 Meg.
Class A amps for all their inefficiencies remain the Standard for the time being. Unfortunately they also are expensive and many of us can not afford to buy or feed them. Also because of their heat production their life span is limited relative to an AB or D amp. 

Oh, I have yet to audition an Atma sphere amp. These are class A amps which may have a longer life you just replace the tubes.