HOW MUCH????
It really depends on how much you want to spend.
There is a BIG difference there. How serious you are about a true 1000 watts. A true 1000 watt amp needs more power supply than your factory alt and single battery can supply. However you can take class A amps and bridge down to as low as 1/4 ohm, orion's for example, and get 1000. It will be HOT and clip if ran long. For a true consitent 1000 watts that you can listen too as long as you want, I would suggest a JL audio 1000 single channel subwoofer amp with an additional battery and a cap. This would be a TRUE 1000+ watt amp that will POUND ANY TWO subs you hook to it. Your looking at about a 1800 setup though. Conversly you can go with other amps ie,,, orion, rockford, MTX, or Kicker, Memphis, etc... Bridge them down and get a rated 1000 but not TRUE. Ever wondered why home audio equipment is rated at 100w per channel or sub amps at 250w and sounds will tear the house down. It is becuase it is TRUE power that has the electrical power to support it. You can have the biggest amp in the word and not right power going to it and you aint got ***t. So my advice is buy a good amp but give it the POWER you need. Most people can not stand listening to a true 1000 watt system. I have gone to bed and woke up with bloody ears becuse of 1000+ watt systems.