Sunrise Restorations is a very good window and i applaud you for seeking out quality opposed to what most customers do: search for cheapness and regret it later( they always regret it).
That said, $600 is a very insignificant amount when you are talking about an investment that will last decades.
Think about it, would life be that much better if you saved a measly 600 bucks for a home improvement project?
I am just trying to put things in proper perspective.

I guess my issue is that I don't see a big quality difference when I look at the specs online for the Okna 500 and Sunrise Restoration. I haven't seen the windows in person, so perhaps appearance is a factor? Any guidance on why one is superior to the other would be appreciated.

My main issue is I want to reduce street noise as much as possible (and have good looking windows too).

I guess my issue is that I don't see a big quality difference when I look at the specs online for the Okna 500 and Sunrise Restoration. I haven't seen the windows in person, so perhaps appearance is a factor? Any guidance on why one is superior to the other would be appreciated.

My main issue is I want to reduce street noise as much as possible (and have good looking windows too).

Both are great windows, so you really can't go wrong with either one, therefore I'd choose the contractor you're more comfortable with.

+1 to ultra - both great windows - comes down to the installers. If they are both equal - flip a coin :)