First, the newest class D amps are damned good, at least my EVS 1200 is, which is the 5th class D amp/s I've owned overt the last 5+ years, BUT, GaN is heralded as the a major advancement in musical clarity, in that it transitions much faster, meaning it's a clearer lens, similar to the finest camera optics, which are similarly expensive
GaN is the newest tech, with lots of R & D involved for audio applications, which makes it more expensive than even the best class D amps. That said, Underwood HiFi has just introduced the Voyager, a GaN amp for under $3K. WTH?
I am in high anticipation of having one very soon. Once I get to compare to my EVS 1200, I will start a thread on it