I know that the higher the voltage the less the amp has to work so a cleaner sound.
That's not quite true.
The higher preamp output voltage allows you to set the gain lower, increasing the signal to noise ratio and
possibly decreasing noise.
But if the amplifier has no audible noise with a lower input voltage, then a higher input voltage won't make a lick of audible difference. And really, with the quality of amplifiers these days....there will be no noise with a high gain setting, so preout voltage is pretty inconsequential and a non-issue in most cases.
And even then...you are not relating them properly. The above is in regards to preamp voltage
output from the HU, this thread is in regards to the input sensitivity of the amplifier. They are related, but not in the way you are trying to relate them.
The input sensitivity range determines the range of voltages that the amplifier can accept and will produce full rated power output with. If the range is from .2V - 4V (for example), then the amplifier is designed to produce full power output with as little as .2V input with the gain set to maximum (all the way up), and with the gain set to minimum (all the way down) it would take 4V of input to driver the amplifier to full power output. It has nothing at all to do with performance or sound quality...just the range of how much input voltage is acceptable to drive the amplifier to full power output.
does this voltage input sensitivity really affect performance?
Not "performance" per say...just where you need to set the gain for a given preamp output voltage.
Should I go with the higher voltage for better sound
Again, higher preamp voltage sounding better is a myth.
And even then, you are not asking about preamp output voltage, but rather input sensitivity.....you are confusing the two, I think.
Examples:Arc Audio- 2.5V
DLS- 7V
JL- 8V
Zapco-???
All of those are great quality amplifiers and would do you wonderfully.
Pick the one that has the power you need, the features you want (such as crossover flexibility, etc) and cosmetics you enjoy at a price you can afford.
Clear as mud ?