id say 1 15 or 18 with a huge box and lots of port area. 1 sub setups are always more impressive to me for some reason.

1500d is a great amp and i cant even push its full potential with my 2 12's, at least not safely

 

i was going with the fi ssds

heres my lastest system



hifonics brutus bxi2010d



2010 memphis mojo 15 inch broke the back this sub need more airspace and to be double baffled

 

Just need more glue on that box and maybe some bracing. You dont need to double baffle for that mojo

 

smaller the box the less it will flex. double baffle is usually used on BIG box's. or maybe if they used 1/2" mdf

 

you can do 2 18's. i was gunna do it i had it all designed. non-wall, only thing is that yea it wont be a wall but no you wont be able to see out the back since the box has to be like 30" tall so at that rate just wall it. i had 1 fi SSD 18 below the window line and it was decent. did 145 with the box tuned at 32 and the mic on the dash (car sealed up)