Stephano,
McIntosh looks at overall performance for each model. Every model but one is balanced as far as inputs and outputs are balanced except for the MC58, 8 channel amp. All of these balanced models will always exhibit at least 40 Db of noise rejection when the balanced connections are used.
Some say there is no advantage of balanced connections unless the circuit is balanced. This is simply not true, performance wise.
Thanks again,
Ron Cornelius,
McIntosh