I would pursue this angle. It's cheap to do, and you'll get instant results. I sealed several big air leaks we had here, and it's now much easier for my stove to keep the house at 70 when it's cold and windy out. If your windows are leaking, try the plastic window film that you shrink-fit with a hair dryer. Applied correctly (you'll need two people,) you won't even be able to tell it's there. These door seals are working great here as well (just touch the door with the bulb, don't press hard or the door will be hard to close.)
http://www.homedepot.com/p/MD-Build...or-Seal-Top-and-Sides-5-Piece-43304/203584938
https://www.google.com/search?q=+3m+window+insulator+film+kit&ie=utf-8&oe=utf-8
