I can confirm a soft and hard reset, hooked up the center and it sounds like bad reception on a radio station.
I'm not clear about what is going on here.
Putting a toy in the port of a sub and retrieving it might just damage the sub driver, but I doubt it. There is no way that event could damage the receiver. The connection is a line level connection.
Now the loose center speaker connection could have done damage. However I doubt it would damage every channel. In any event it would blow the power transistors and make the receiver go into protection.
I think you are trying to tell us that every speaker is distorting. But your last post suggests it may be just the center speaker that is distorting. Which is it?
If every channel is distorting then most likely there is a failure in the power supply and that would be that you have lost either the +ve or -ve rail voltage, so you are getting either only the positive or negative deflections over or under the zero line.
If that is the case then repair might well be worth it, as the most likely cause would be the failure of a voltage regulator in the power supply.
One thing I can be certain of that the toy episode is a complete "red herring" and nothing to do with this.
What is he receiver and how old is it? You are not going to replace a receiver for $200.00.