[Cykomiko]

Just wondering why Nuprime has dedicated mono amps besides the stereo amps in the 10, AMG and Evolution series but not in the 9 series.

The 9 series stereo amps can be bridged into mono amps but is the sound just as good as if they were dedicated mono amps or is bridging somehow inferior to dedicated mono amps?

For the AMG series where both options are available, would it be preferable to run two AMG Ones or two AMG STAs in bridge mode?

[rustydoglim]

Bridging from stereo to mono is not as good as a mono-only design. But it also depends on the amp's design.
The 9 series objectives are valued for money and performance, whereas we emphasize performance before cost for the AMG and Evolution series.
Indeed, a bridged mono can perform nearly as well as a standalone mono design, but it will cost more to implement.
The AMG STA is such.  Some people don't like the smooth and warm sound of AMG STA, so we designed the neutral and faster AMG One (it is "mini" version of the Evolution Two)

You should focus on the sound characteristic to choose between AMG STA or AMG One.