New member Looking for advice!

Hello all

I live in okinawa Japan in the U.S. Air Force. I have a Silvia s14 and have recently put a system into it. I am going to be using the hole where my rear seat covers to put my subs. The question that i have is this: I can put 2 or 3 8" subs there but only have enough room for about 1.2 cf for a box. I am running a precision pwer pc 2600 amp for them. What subs do yall recomend and what type of enclosure. the amp can put out 600x1 @ 4 ohms bridged. I am relativley new to this so any input is greatly apreciated! I am looking at spending around $500 for the subs max. I just want something that has a good amount of bass to it. A friend recomended running 2 kicker 04sl87 4 ohm subs. Anyone? I attached a couple of pics so you guys could see what i am talking about. the speakers you see are 6.5's. Thank you all in advance!

Sully

Here is the space that i got:

From the top of the sub box to the back of the amp rack is 7.5 inches

From the bottom of the sub box to the back of the amp rack is 9.6 inches

The hole measures 9 inches

If i cut the surround off the trunk hole i get .75 inches.

Would 3 8's sound that different than 2 10's? All i have ever had before was 2 12's and 1 12 setups. Thanks again yall!