input sensitivity

An amp with high sensitivity is more prone to noise pickup in the interconnect. I prefer to boost the signals to a good high level before sending them through my (admittedly long) interconnects. However, with good wire and good electronics noise should not be an issue, but the oversensitive volume control, mentioned by Aball is a problem.

The input sensitivity of the CarverPro ZR1600 that I use can be changed by moving a jumper plug between four positions.
0.316 vrms...common in consumer electronics with low voltage unbalanced outputs.
0.775 vrms...most common line-level calibration.
1.23 vrms...commonly seen in professional audio products with balanced outputs.
2.45...Devices with large voltage swing used to drive long line-level paths.

These signal levels produce full output: 600 watts into 4 ohms. I use 2.45 vrms.
The descriptions are from the owner's manual.