The Simonton web site has some fairly good technical data, but very little prose describing the windows and the benefits of the various options. They also have some outright typos and missing options on some pages. They don't promote it very well, but the 9800 series has options for triple pane, krypton, and the higher-end SuperSpacer. Check the glass options listed at the link below and the thermal data link. I just installed the 9800 windows on my own home, so I'll be happy to help in any way I can. You should find that the 9800 is much less than the $1000+/window NES is wanting.
http://www.simonton.com/homeowner/produ ... location=2