To see what a well engineered window looks like, study the architectural details at the Marvin Window website. I always feel safe recommending Marvin.
There are many other window companies with different prices and styles. You need to browse through and find what you like and what fits your budget. Ask local suppliers for prices on individual windows. You can bargain for a discount when you order many windows at once later.
http://www.andersenwindows.com/
http://www.integritywindows.com/
Here are the qualities of a good window. 1. No air leaks. 2. Exterior surface will endure in heavy sun and rain. 3. Interior finish fits my taste. 4. The hardware is durable and firm. 5. The window opens up firmly but smoothly. 6. There is no visible caulking, but clean corners. 7. The style of the window fits my house.