I have a pair of 12" CVR dual 4-ohm subs. I am pushing them with 400-500 watts RMS each. They are in a sealed box, common chamber at 2.50 cubic feet, 2-lbs of Poly-Fill. They are loud and clear.
What model of amp is that Kenwood? That 1000 watts is most likely peak, which you ignore. Always go by RMS. He is right, the L7 and the CVX is basically the same, one round (CVX) and the other square (L7). L7's are good for SPL, though you can get good SQ from one in a sealed box. For the 15" L7, a 4.5 cubic foot box, tuned to 34 Hz is good for a daily driver vehicle. That is from someone I know that works for Kicker, in OK.