We went to bed around 2100 in hopes of being asleep before they started the noise, but I had no such luck, even after taking a melatonin. By 0330, visions of poisoned sugarplums were dancing in my head. In addition to dueling stereos, they were singing mariachi songs outside, howling ("ay-yi-yi-yi-yi") and imitating the noises made by passing cars, including one police car earlier in the night. Sadly, it was not for them; we live near a major intersection.
A half-awake Vogon told me that if I was going to call, to go ahead and do it or else I wouldn't get any sleep before the midget woke up, so I called 911. (I hate to do that, but a recent flyer distributed by the complex management stated that residents should call 911 and establish a police report for off-hours noise complaints instead of calling management.) Ten minutes later, the noise was gone and the responding officer let me know a second noise call will result in a report and a ticket. Afterward, I got a solid six and a half hours of sleep, which was rather nice for my immune system.
Hooray for the justice system working. (: