I have a Sundown SAE-1200D on my sisters 15" AQ HDC3 in a 4^3 @ 38hz and its perfect, you don't NEED more power than what they're rated for, but everyone loves putting more to them, because they CAN handle it.
I will have a 250A alt, 1 Hawker HX300 in the front(street A legal), and two deka Intimidators in the back. I have 4 runs of 2/0 as well. Its still a lil on the weak side, but i may go dual alts in the future.