Hit up Rusty and see what you can get for $400. I'm not sure how much the LV3s or LV2s cost but either way I think you should go with 3-10s. 3 d1s can be ran at .67ohms (I think), which the AQ can handle just fine.
3 12's would take 4.5-6 cubes... 1 18 would take... guess what... 4.5-6 cubes.
im guessing your talking about a dodge ram standard cab as its the only standard cab i know with that kinda room (i had one) if you wanna run a single 18, run a single 18, there is plenty of room. take the back panel off... break out the tools and remove the center seat belt track (otherwise you have to build a C-channel around it) you can go 60" across, 11" deep and 24" tall without messing up how far you can push your seats back. thats 10.25" of mounting depth and 7.23 gross cubic feet. 24" inches takes you right to the window line and not hair over it so you will not have to worry about not being able to see out your back window, enjoy
I wouldve but its D1 man.. and with my electrical right now I dont feel comfortable running .5 ohm daily on my 2200. a fried amp right now would kill my plans