what to buy to replace my Anthem P5 ?

[Cos]

Ground hum ?

Which ATI amp?

I wonder if class-AB is more prone to hum than class-D.

He had the 6000 series which I believe is Class D, but you would definitely know more

 

[AcuDefTechGuy]

He had the 6000 series which I believe is Class D, but you would definitely know more

The AT6000 and AT4000 series are Class-AB.

The "NC" series are Class-D.