First thing to note is your speakers are nominal 4 ohms.
Most amplifiers which are stereo, when strapped to mono are NO GOOD at 4 ohms.
The Hegel are the same, They are rated well at 8 ohms in mono configuration, but cannot be used in mono configuration with a 4 ohm speaker. (they are rated at 4 ohms, but only when used as a stereo amplifier)
The Bryston 7B3 ARE designed to be used with a 4 ohm speaker, and have 900 watts at 4 ohms.
Most amplifiers which are stereo, when strapped to mono are NO GOOD at 4 ohms.
The Hegel are the same, They are rated well at 8 ohms in mono configuration, but cannot be used in mono configuration with a 4 ohm speaker. (they are rated at 4 ohms, but only when used as a stereo amplifier)
The Bryston 7B3 ARE designed to be used with a 4 ohm speaker, and have 900 watts at 4 ohms.