Hello Dash, thanx to you too for the comments.
The subs facing the tailgate: I would like to tell you that its all to do with acoustics and all that but to be honest the reason is purely cosmetic. You could have then facing anywhere in the boot as they are in ported boxes, you would get little or nil sound difference no matter where they were located. However, if they faced the rear seats, which some people do, they would almost definately rattle the seats and add distortion to the equasion. I suppose you could also add that the sound would reflect and bounce from the rear hatch therefore making more sound per foot of free space, Like done with the 6x9s in the rear shelf, positioned to bounce the sound around from the rear window so filing the available space with sound.
The sound from Bass speaker can be both heard and felt due to the low frequencies, think of your neighbour when they have their music loud, you can usually just hear the bass through the walls of your house. So a big YES, you can hear the bass clearly when the parcel shelf is in place.