Explorer needs to bump!

[RF4LIFE]

I have a 2004 Ford Explorer without the third row seats, I want to make a box that will fit in a 32" x 45" x 24"-36" space (20-30cubes max). I have a Rockford T2k and it puts out right around 2500w RMS @ 1 Ohm, this in mind I only want to use this one amp for my subs. I have 4 Rockford T1682c's in the doors and 8 Rockford T162c's in the back, so I have extremely clear mids and highs. My question is should I get like 1 large 15", 2 smaller 15"s, 1 large 18", 2 smaller 18"s? I don't know what will sound the best? And I don't want my doors to drown out my bass. I am a daily driver but I want to get the most out of what I have. I was thinking maybe 1 15" or 18" Fi Sp4 but I don't know if maybe 2 smaller 1000w RMS 15" or 18" drivers will be better? Recommendations?