My current house was $150K, is 1,400sq.ft., and has 3 bed rooms and 1.5 bath rooms. There isn't really room to add a second full bath room for my kids. Perhaps a shower stall could be squeezed in to the downstairs half bath room, but it would be very cramped. The laundry is also in the basement, so it all has to go up and down two flights of stairs.
We have already replaced the roof, windows, some carpet, upstairs shower, bathroom flooring, garage door and opener, and other smaller things. at least in this area it seems like you don't get very much of the money spent on improvements back out. We could continue doing things, but would never be able to fix the lack of a second full bathroom and inconvenient laundry location.
A new house would be 1,500-1,600sq.ft., and have two full bathrooms. Perhaps a ranch style. Laundry would be located near the bedrooms. A new house would probably cost between $250K and $300K.