To add to fmw's truths: Amps with linear response, low distortion, low output impedance, and operated within their clean power limits do indeed tend to sound the same. When these conditions are not adhered to, actual audible differences can and do occur.
Jack, you need to compare the repair and maintenance cost of the older amps to that of new. If you have access to a reputable repair shop, that route is often less expensive than new amps (depending on the repairs involved, of course). From your first post, your shop is kinda pricey, and the time and hassle compounds the expense. If I were you, I would ignore any sentimental feelings for the old amps and go with new (or at least newer) gear. Emotiva amps are quite good.
As for newer than what you got but used, I know a person selling an ATI AT2007, asking $2250. I think the warranty is transferable, not sure, but that would replace seven channels of those old Yamaha amps and do an outstanding job of it.