James,
With this new SP4, the overall depth of this unit is 19.25 inches.
This depth dimension is larger than most of the current Bryston amplifiers, except the 28B.
I am not sure about standards with A/V rack dimensions, but this will be a problem for my A/V rack - built-in cabinet, not to mention the wiring connections at the back that need additional space.
And the question is if there could be a reduction in this overall depth dimension by say 2-4" inches that would be similar to the current SP3.
Luigi