During installation of System 7.5 Update 2.0 on a Power Macintosh 9500 series computers, the old Sound and Monitors control panels are mistakenly not removed.
The presence of the older control panels won't disrupt the operating system, but you can remove them to avoid confusion.
However, you may want to consider that the Monitors & Sound control panel does not provide a way of recording system alert sounds. The SimpleSound application does this, but it is not included with System 7.5 Update 2.0. So, to record system alert sounds, you need to use the Sound control panel. With this in mind, you might want to leave the Sound control panel installed.