I used to work for Pella windows in Greensboro. I replaced every window in my house with Pella, and for the new construction sections, I used Pella Designer series (wife wanted the blinds in the glass). They are some of the easiest windows to install with their fold-out nailing fins. The warranty on the windows has expired, but they are still perfect. Mine are wood frame windows with aluminum clad exterior.
For the replacement windows and the front two new construction windows, I used Thermastar by Pella that I bought at Lowes. For a low price window, they are very efficient.
What material are you looking to use? (vinyl, wood, fiberglass, etc)?