I don't know why you wouldn't fix it! My family ran a studio off a similar spec system for years. An A4000 would only gain you a couple color wipes in the Toaster, and you'd need a HighFlyer or similar expansion case to hold all the cards and drives.
But if you don't, I'd happily take the Spectrum, PAR, and TBC off your hands.
I'd actually troubleshoot a little differently. Some revision motherboards have a fuse near the port. And the first chip I'd pull would be swapping the two CIAs - I forget which is which, but if the mouse starts working you can look up the details to figure out which to replace.
Both of those have happened to me on various A2000s when I was a kid. It is usually caused by plugging in mice or joysticks with the power on and shorting pins. This seems more likely than a chance failure of some other chip.
