I recently just upgraded my home with the Simonton Daylight Max windows with the sound control package and super spacer and wanted to give my two cents. Like the original poster, I live in a noisy neighborhood with a busy road. My house originally had some low thickness (1/4" or less) Milgard Style Line dual pane windows installed when I bought my home. I was told that the Daylight Max sound package uses 1/4" + 3/16" offset glazing set up to block noise. I don't think Simonton publishes their STC and OITC ratings like Milgard does, but I estimate that after installing the Simonton sound package windows, I got a 5-10 dB average improvement in sound reduction when using a sound meter to measure. The Simonton Daylight Max sound control windows still won't block out the loudest, low frequency rumbling trucks when they pass by, but I understand most windows will have a tough time with that.
+1 on making sure that your windows are correctly caulked and sealed at the edges. My installer put the new windows on but needed to go back to the office for a few hours before finishing. That gave me time to compare noise levels. Once they caulked the windows, there was a noticeable difference in sound.
Q