Sub Recommendations

I think I decided on an amp to buy: Hifonics Gen XI Hercules, 1500x1 @ 1 ohm. Are these amps underrated at all, and if so by how much?

Also, what kind of sub(s) would you recommend for that kind of power. So far, I have a few ideas. I can do 2 IDQs (10"s or 12"s), a single Digital Designs DD9515, Kicker L715, or maybe Adire shivas or a single Adire Brahma. Give me some opinions, please. :)