well here is what you can do...
first if you dont have any sound deadening in the trunk then get it done. underlay of jumbolon are two good options.
then buy a full sheet of Lasani wood .5" and floor your car trunk with it, double story. have a trap door kinda thingy in it for the spare wheel. flush mount the amps between the two lasani layers, you can remove the covers to show off the circuitry. use .5" plexiglass to cover the amps. you can also have 2-4 pc cooling fans installed at appropriate location to keep the amps cool. you can also have a box built like the one you showed me. since you are looking for a SQ system, you will have less volume to worry about. and then you can cover everything in carpeting material or leatherite.
Lasanii wood sheet .5": around 1500 rs per sheet i think
Plexiglass for cover: ~1000
cooling fans: 150-200 each (i think)
sound dampening:~500 rs
floor making: 2-300 rs carpenter charges
carpeting/covering: material dependent
estimated time to get it all done... 2 days-2 weeks.
or you can have two separate sealed fiberglass boxes made for the woofers and install em in the area right behind the brake lights. the amp can be mounted on the back of the seats.