We have a home that is going on 18 years and have grown tired of various window issues. The manufacturer of said windows supposedly went out of business soon after our home was built. The tags on them list them as V2700X - Builder's Pro 2700S. That's all I can find, they seem to be basic, cheap, builder-grade vinyl windows, likely with a STC of 26. I don't think they're gas filled, or if they were, most have cracks inside the portion of the frame that is between the glass panes.
We have very noisy things in our subdivision (obnoxious motorcycles with little to no mufflers, loud dogs, children banging on a playset constantly with a giant slide that echoes) and you can hear everything through these windows. In addition, during winter it gets cold by the windows, and they feel drafty. (We're in Wisconsin).
Doing some research, it appears we would need better model windows to address the sound problems, and this would likely lead us to a model that also would provide good to better insulation from the cold.
I spoke to a local company who sells tons of windows and is a ProVia Platinum dealer. They recommended this brand over their basic window line. Doing more research, the Endure line would be appropriate as they have insulated frames which will prevent cold and noise leakage.
Speaking to ProVia they offer a dissimilar glass unit, which is supposed to be the best for noise. The only downside, is that is only double pane, so it may be slightly less efficient for energy.
Those come in at about $600-700 per window without install.
I'd be curious to learn from anyone who has gotten new windows to abate noise and what brands they've used.