My parents just went through the same process. They ended up going with custom windows from a small local company there in Texas. However, I would say that installation is about as important as the product itself for this particular project. If you have great windows with a great warranty that aren't installed just right, they will transfer a lot of heat and waste a lot of energy. Therefore, check references and find a great company and maybe work backwards with the products they offer or have experience installing.
Steer clear of the guys who claim to sell you direct from the factory.
I would suggest you contact your local lumber yard, NOT the big box apron wearing stores for contractors and products that would fit your needs.
Although many of the lower cost windows seem to work well. Its really all about the quality of the install that makes or breaks how well the window performs. You can have the most expensive window on the market and if its installed wrong. It would be the last time you ever would think to purchase that brand again.
Also Federal laws require ALL contractors who are in the window replacement business to be licensed as lead paint renovation contractors. In fact all home improvement contractors must have this license as well. If they do not have this license and cannot prove to you that they have them. Do not use them. If they get caught doing your home without it they can be fined over $30, 000 which could prevent them from coming back with your windows the next day. If your home is older they must test for lead. They must work in a contained environment, They must post signs that lead dust is present, They must maintain detailed records on the projects they work on. They must provide you with a pamphlet called "Renovate Right" and you must sign off that you received it. And if the house ever had a child or adult that has suffered from lead paint poisoning they must be Lead Paint Remediation certified to do this work.
There may also be a "mom and pop" type shop in your area. These places may carry some of the bigger brands and have a list of contractors that install for them...its a good place to begin your research.