Or you could just buy this one...
ZX1000.1
It is rated 600 @4 ohm, 1000 @2 ohm.
****If you have only one JL sub, and it's a d3 ohm, how are you planning on running @4ohm?
If that's rt, and you have one d3ohm sub, then you can run at 1.5 ohms or 6 ohms.
My amp would be PERFECT @1.5 ohms, and will do more than rated 100% GUARANTEED!!!
If it's a d1.5ohm sub, then you can wire to .75ohm or 3 ohm. Any amp that is 1ohm stable would then be what you wanted.
Actually that should open the door for you to a lot of options...