The last number I heard was that krypton is currently about 600 times the cost of argon. Using krypton in a large window can become very expensive. In order to achieve the maximum effectiveness of krypton you need a narrow airspace between the glass - roughly 1/4" or so. How big is the largest individual sash in this garden window? In a really large window, a very narrow airspace can become a problem because there may not be enough room between the lites to avoid them touching during changes in barometric pressure - this may be worse in a triple than in a double. Depending on your environment and on the level of energy performance that you desire, using argon (double or triple) in a wider airspace can result in very similar energy performance numbers, compared with using krypton, often for a good bit less money. And a wider airspace (1/2" or so) is better in a larger unit. Ultimately though, the gas infill is a good deal less important than is using the right LowE coating on the glass. With the LowE coating you can control the level of solar heat gain thru the window (from a lot to almost none) and keep "regular" heat inside your home in winter and outside in summer.

Couple of things worthy of note: Triple pane provide no additional sound attenuation over good double pane. The Pella 350 is a decent window but nothing better than other good vinyl options and worse in some comparisons. In the DH, they rely on pocket sills which is not ideal but all yours are sliders so they will all be pockets. What do you want the windows to look and feel like? There is probably a bit spread between wood - fiberglass - and vinyl.

Your choice of the Schuco window is fabulous. I've been one of the Pro's on the forum posted above and it's sister board for a long time. The Schuco window has been window of the year many times over. It's German design has established a new look with great ratings in our industry. The window is manufactured with high standards in design, functionality and performance. The inline slider they have is a marvel of the industry. Schuco has the lowest U-value in the industry due in part to their exclusive TPS (Thermo Plastic Spacer) seamless spacer system and 99.9% Krypton filling system. It's a warm edge IG sealing system, which is exclusive to Schuco. I also agree with Skydawggy on your pricing. At $550 a hole your getting the best window in the industry at half the price it's going for around the nation. But keep in mind the window is only as good as the installer. We preach this to everyone across the land. It's hard to know if they're done properly for the standard consumer. Just make sure everything is to your satisfaction before making that final payment.

I had the first window company visit the house yesterday. He referred to my existing “single strength” windows as “$3.00 windows” and said the installation was awful, it’s no wonder I hear so much outdoor noise. He feels the basic glass option from Marvin, with proper installation, will make a noticeable difference but based on my comments would recommend their sound reducing option. The second company I’m meeting with later this week was recommended to me by the local architectural rep from Marvin. Unfortunately, I’m already not feeling solid about this company. The salesman didn’t follow up with me during our first interaction and when I mentioned it, he placed blame on the Marvin rep. Also, when I told him I would be comparing him against other companies he started with the scare tactics about most local companies don’t have certified installers. Seems like a fast talker to me, which put me off. Will have more details about the windows later this week.