Penny's does have good deals. You need to ask the people working in the draperies department when they will be having some kind of sale to get your cost down. Oh yeah, before you guys get the idea that I am some kind of interior designer, I should tell you that my wife worked in that department at Pennys.
They will ask you about the colors in your room. (Take some samples from the room with you, you will never get the color shades right without it.) The thing you may not be ready for is the cost. The window in our family room is close to the size you described and we spent $400.