Hi, Chooch. Welcome to the forum.
Wm. Knabe made and makes good pianos. I'm a fan. The one you're looking at, however, is too old. Pianos don't improve with age. They degrade, just like any other mechanical device. Fifty years is just too old. The good years are behind you.
Here are some general guidelines: Play lots of pianos. Give yourself (or your son) the chance to find the touch and tone you like. If you buy used, try to stay under 10 or 15 years. Big pianos sound better than little ones. Avoid spinets. The action is difficult/expensive to service. If you find a used piano you like, have a tech with no connection to the seller check it out for you. Visit all the shops in your area, check Craigslist, Pianomart.com, want ads, whatever is available. Be patient. It may take a while, especially if you're shopping used.
We have several forum members who are dealers in Florida. Last month, I visited M.O.P. at her place in Ocala. They had tons of pianos, new and used.
www.fortepianogallery.com Nick Mauel's place is in North Venice.
www.nickspiano.com I'm sure there are others. I just don't recall right now. Anyway, give them a call and see what they have.
Are you open to a new piano or are you just shopping used? What kind of budget? The folks here like piano searches, so hang around and ask all the questions you like. And good luck!
Charles