you should look into the aq hdc3 18's and get another ap1500 and that should leave you with some where close to a grand left for your electrical upgrades and box materials, and trust me the 1000 watt rms rating don't mean nothing mine are eating up my fosgate 1000's but i have to up grade my electrical before adding more power, and i'm not sure about how much space you have but if you can't give them 5-6 cubes net each then maybe look into doing 2 of the 15's or maybe spending a little more on a single 18 that would like 3000 watts in a daily setup