"If the input resistor material is a source of hiss" is the key part as to whether or not there will be a noticeable change. Also, even if it is a source of hiss, if there are other sources that are worse, you might not be able to tell the difference. I use MF for almost all resistors in an amp, so I don't generally have any hiss issues.
Besides that, you might need to record a before and after sample to tell the difference if it's a mild change.
Always good to tidy things up.
