Right, as ya say ignroing they are the work of the devil lol;
Measure your parcel shelf, go down to homebase, get some 10-14mm MDF for about 10 quid thats the right size.
Get it home, get out your parcel shelf. Draw around this onto the mdf with a pencil. Cut out around this line, but about 5mm outside of the line, with a jigsaw.
Now the hard bit, a hell of a lot of sanding. Use an electric sander and take your time getting the side nearest to the back of the car at the right chamfer for the boot.
Then cut out holes wide enough for the speakers. Also make two small plates of mdf again with the holes but this time so that they can be screwed into this plate. They will then sit in the cut out hole in the main shelf by attaching the plates to the underside of the shelf with a strong wood glue or some screws or both. Put some kind of strong materil over these holes from the top, eg thin mesh. Screw some large screws into the far sides of the shelf, where the hangers are. Wrap these in black insulation tape until they are big enough to slide into the slots.
get some felt from a diy store and glue it on, staple it tight around the bottom. Obviously it will go tight over the holes for the speakers. So it will look like a normal shelf and you wont get broken into or look gay lol, and your not gonna have to pay 60 quid plus for a 'stealth shelf'. Ive done this myself minus the 6X9 bit, and it looks much better, allows me to have a decent sub box in the boot and doesnt shake and make gay noises
Alternatively screw em into the std shelf, but they will sound like someones hitting a baking tray with a wet flannel and they will be in plain view.
Electronics wise, id reccomend getting a few metres of decent speaker cable and connecting these to the HU, then taking them down the car and into the 6by9s as the std rear cables are thin and shite.
I had some 6by9s that came with the westy and bought a few metres of cable off
www.caraudiodirect/com, it was the CAD silver stuff for £1 a metre, just until i got a sub.