I have two 12" Dual 2-ohm CVX subs powered by a Hifonics HFi2500 at two ohms. They should be getting around 700 RMS a piece from that amp and they're in a prefab box from Amazon. I'm pretty sure it's the box, but these subs just don't hit lows. It sounds really airy and they flex a LOT when I put it on a low song turned up. Each sub has 1.5 cu ft of air space in the box which isn't that much. I want to have a good range of bass, but I'm playing songs with higher frequencies to make them sound good. I'm not going to lie, these subs get LOUD, but I know there has to be more potential out of them. Any recommendations? Should I just make a bigger box?