I've been told my a few contractors that something in the lines of a 80+ efficient furnace and the goodman are a good choice for someone that wants something good and cheap, not major retrofitting of exhaust ducts etc and plan on selling soon.
The next person down the line will be happy with at least 80 and shouldn't decide not to buy because of it whereas a really old system they might move on. However, they will want to hear that magically 90+ in their ears and 'new furnace' before the sign on the dotted line too.
If you were SURE you were moving in 3 years I would do just that. Because the extra cost you will have to pay for something better will never be justified.
However if you were going to do it right, I would say 90+.