I have nothing to add except these were the cocaine dealer cars of my high school era and it's weird (to me) to see them going for $2500 nowadays. If I were in the market to pick up a fixer-upper Winter beater this would be perfect.
We have dogs that shed a lot and my furnace is in a closet in the garage. Over the Winters I admit I don't like changing the filter because it's cold and I have to take the entire thing apart to do it. Anyways, my fan motor recently went out from having to work harder over the years to pull air through a filthy filter. It cost me $273.. if you add labor into that it's most likely over $500 (a friend and I did it ourselves).
So yes, using good filters (and changing them regularly) is worth it. Randomly waking up one day to a frozen house absolutely sucks.
Why don't you make a list with three columns: Options you need in a car, things you want, and things you don't want (create these without any makes in mind). After that, you can narrow it down and maybe people can help you better.