My guess is you will most likely need another amp. In my car i have 2 10" kenwoods powered by and am and then 4 infinity speakers powered by an amp. I know that once i pass volume level 15, the bass doesn't get much load but the speakers do. So i think if my speakers with an amp are still overpowered by my subs that you will need at least that.
maybe not tho.. idk.
2006 G6 GT
Mods so far: Black arrow overlays, Chrome recessed grilles, Blue LED license plate light, Blue LED reverse lights, Smoked tails, 20% Tint all around, Red led's for the interior, White led dome and map lights.
Sound System: 4 Infinity Kappa component speakers, 2 Amps (950w total) and 2 10" Kenwood KFC subwoofers, 7" touch screen Pioneer DVD
Performance: Mobile 1 oil, Mobile 1 oil filter