Agree with most all of the above, except a little nit.
How are they going to "sound like crap", unless they are run off a phone or have some other physical/electrical defect, or in an airplane hangar....... If so, well, that's a problem.
Cosmetics are about 75% of the game these days in vintage resale. (sorry to you naysayers)......everything else is easily fixable. Not cheap, but fixable.