I would only replace the resistor if the amp is not sounding right, if you have enough highs coming out then leave it.(Maybe clean up the mess a little bit)
If you do decide to change it then you might need a higher wattage for the resistors you put in, and then you also have to make sure that the L-Pad can manage the higher load as well.
I am presuming the pot you mentioned is a L-Pad or a wirewound high power potentiometer that controls the tweeters.
The 50R resistor might have been a late change in the factory or it could have been performed as an upgrade or recall from the factory but performed at the local service center.(back of the local music shop).
If you do decide to change it then you might need a higher wattage for the resistors you put in, and then you also have to make sure that the L-Pad can manage the higher load as well.
I am presuming the pot you mentioned is a L-Pad or a wirewound high power potentiometer that controls the tweeters.
The 50R resistor might have been a late change in the factory or it could have been performed as an upgrade or recall from the factory but performed at the local service center.(back of the local music shop).