This might help give you an idea: http://www.teambeachbody.com/eat-smart/nutrition-tools/caloric-needs
It all depends on what your goal is, but I personally wouldn't go below 2,000 for an intense program like P90X. You guys eating 1,500 or less, I don't know how you have the energy!
I"ve tried to hit 2,000 calories and when I do, I just feel FAT. Like really heavy and lethargic. Even when I work out, I still feel gross. When I wake up the next morning, I feel disgusting as well.