can't really answer you without knowing what you consider your piano shopping radius from where you are, and whether it includes a major metro area where folks with nice grand pianos are 'downsizing' or just liquidating. in my area (northern calif, u.s.a.) that would be very high retail and not likely to find a buyer very quickly. only you and your spouse know why she's fixed on a model M. with more than 50 k. to spend my preferences in steinways would go to model O or L or A. but she might be set in her mind, and you might feel pressure to please her sooner rather than later. for some folks, spending an extra 15-20k. is worth the immediate gratification. many instruments as old as twenty or thirty years or more still have all the original parts, and the best restorers and technicians are extremely meticulous about what replacement parts they use. they'd also be able to assess any used steinway and tell you if there's any problem with it, what its ceiling potential would be after some care and attention, and how much corrective action would cost. the more options you leave yourself as a buyer the better chance you have of finding a realistic price, unless you are in a very restricted market without many choices.