This logic never made sense to me. Repairing or replacing based on the costs to repair. nope.
it is math.
If it would take much more money to replace this piece in order to achieve the same or better sound quality, then repair it. Stop worrying about the costs to sell it.
For example, I work on cars all the time. Restore and repair. If one really loves their car and has taken care of it. proper maintenance, etc. and the car develops an engine issue that requires the engine be rebuilt, then rebuild the engine. Because if you go in the direction or replacing the car with a new car, you will come out of pocket for a whole lot more money. So rebuild it or replace the engine with a rebuilt engine. Unless one just wants a new car and new car payment.
If you were totally happy with the amps sound in your system and to replace this amp with a new one that is as good or better, would costs lots more??? I don't see the logic here. fix it. However, if you can find a quality amp that is as good or better for the costs it would take to repair yours, then okay. go for it. But, I doubt you can.
The math doesn't work for me.
But, if you are itching to upgrade, then that is the audiophile story and have fun.
enjoy