However, it's not that remarkable.
10 amps at 48 volts is close to or more than 40 amps at 12 volts.
4 amplfiers on a 12v system, at 40As each, yeah, that's a lot of current.
I mean, you can only convert so much power, and believe it or not, 100% efficeincy is the maximum theoretical conversion.
That said, there are some new high-efficiency chip amps from Fosi (I just acquired one), and Helix has a new line of chip amps that are exceptionally clean, albeit almost sterile in reproduction.
I still think that conventional board designs with the use of high-efficiency chip-driven fast switching on-demand variable power supplies, along with GanFETs, have a good chance of being the next big thing.
If it is reasonable, sounds as good as one expects, and does more for less, bring it on!