I decided on the Simonton 9800 "Impressions" series. They are a nicer-looking window than the 5500 "Reflections" line. I added the Glass Sensor upgrade package that includes 1" glass, Low-E, Argon and the Superspacer. I also added reinforced meeting rails. The difference in price between the 9800s and the 5500s was only a total of a few hundred dollars and the 9800s come with a better warranty. Check out www.simonton.com for pictures and more detail.
The windows went in the week before last. The difference compared to our old single-hung wood windows is astounding and they look very nice. Check out my post, "Man these Simonton 9800s are Nice" that I posted about a week ago.
You can't go wrong with these. If the local contractor or distributor isn't familiar with the 9800s (and many are not yet, as it is only recently been made readily available), ask them to contact their Simonton rep. An upgraded 5500 will perform similarly and may be even less expensive than my quote (contractors vary significantly sometimes) but I think it's less attractive.
I also considered the Alside Sheffield and the Great Lakes Uniframe, both of which were quality mid-grade windows. The Alside was cheaper but the sales experience was poor. The Great Lakes was about $3000 more, although the contractor was good. I also looked at, but quickly dismissed, the Silverline 9500 and the Accu-Weld Epoch 2300, neither of which impressed me. Of course, installation IS everything, so find a good contractor first. Good luck!
800-399-4623