The HPA-S500NC replaced my beloved Audiolab 8000M amplifiers after 16 years in my setup, driving my Nubert nuLine 264 with ATM. This power amplifier is fed by a NAD C658 Preamp/DAC and it fits like a champ in this setup. "It doesn't sound" is by far the best compliment i can give. Very clear and linear sound and plenty of power.
The chassis quality is good and better what i've expected from the pictures. It's massive with no bells and whistles and serves its purpose perfectly. The connectors are really solid and provide good stability for any kind of cable. If there is anything to complain than probably the bright power lightning, sensitive people might get irritated, but for me it's not a problem.
In summary, a big recommendation from me.