Choosing replacement windows

Hello
I'm new to the board and need help in choosing windows in Colorado. What matters when choosing: doublepane vs triplepane; DP certification; whether frame should be insulated with foam; warranties; and questions within and among manufacturers.
For instance, I was interested in Vinylmax's Hyde Park, but the salesman said the "affordable" Easton was just as good, but did not quote price for the Hyde Park. Also, trying to decide among Vinylmax, Window World and Plygem. We're on a fixed income and want to get a good window at a fair price.
Don't know whether it's worth the 1500-2000 price difference we've been quoted.

Any help would be appreciated. Thanks

Search the site for Colorado. There are several exhaustively detailed posting from people in Colorado that went through the selection process in detail.

That will be a great place to start.