I would put aside about 100 for the box and wiring kit for the amp. What is your goal with this system. Are you looking for sound quality, just plain loud, or a little mix of both? Do you care what size/how many subs you have? What type of vehicle is this goin in?
2 12" orion hps with an interfire 1000watt rms amp. No eletrical upgrades are needed they all have good factory warranties and that will leave you with like You will have almost 400 left over for wiring, cap, box, and extra batt if you feel necesary. My buddy has this setup and it sounds amazing hits nice and tight with the music and can still hit the lows good. For under a grand its a nice clean system.