Good decision to dismiss the Alside Mezzo, it's really not a window that should be considered by most homeowners with a reasonable budget and an interest in buying windows that perform well year after year.

In an environment with extremely cold winters, keeping indoor air in and outdoor air out is particularly important. Okna's Air Leakage rating is one of the best in the industry, making it a great choice.

The second part of the equation is getting an installation that doesn't undermine the performance of the window. If your quote on Okna is from HomeSealed, you've found one of the very best. If it's not, I'd recommend getting him out to see how his installation stands out from the competition.

I wouldn't put much stock into the idea of something being made specifically for that guy.

Get a CPD number and compare the products that way.

In your climate, no reason I wouldn't be looking at triple pane as an option.

Be sure to compare air infiltration rates as randy stated as well.

The problem i have with Thermal Industries is the fact that they utilize a pocket sill or snap in sloped sill on their windows. Do a search of some of the pro's on this board and a few others and you will clearly see its not well regarded.