Yeah, that's almost a good idea, but not quite.
First, mounting subs in that location would certainly require removing the rear parcel shelf and doing a significant amount of sound reinforcing, as that set up would make your rear deck rattle like hell.
Second, that's a complete rip off. You could buy much better components, have it custom finished in your matching trunk carpet, and have it professinally installed for less than $1500. Geesh, the nerve of some people to charge so much.
My set up for instance works well. I have a single 8" sub that takes up little to no trunk space [it's opposite my battery and takes up about as much space as the plastic battery cover on the other side]. It's Kicker's top of the line sub, Alpine's best line of amp, it's covered in matching trunk carpet, and it cost much less than $1000.