I need to replace old energy sucking windows in odd sizes.
Also, odd sizes make the price go up.
Your best bet is to start calling replacement window companies in your area and ask them to come and give you a quote. Some examples are: Pella and Renewal by Andersen.
Get windows with a good warranty. If you can't afford to do them all do 2 walls and replace more with the same brand when you can afford more.
You can also go to a "home improvement" expo in your area because the dealers are there and usually have some sort of sale going on in conjunction with the expo.