Front Speakers:

Remove the door trim (door card) and there's a cavernous hole that easily accepts 6"-7" woofers. Its also rather deep (especially with electric windows !) so you can get away with a larger motor structure in the doors.
The only think stopping you from installing your 6"s in there is the map pocket and lack of hole. So remove the map pocket (held on with 5 screws) and the carpet trim panel around it. Make your own carpet trim panel out of 6mm MDF, punch a hole thru the MDF to line up with the hole in the door fram and voila ! Instant 6" into the doors. Trim the MDF with carpet or leather or whatever takes your fancy (just glue it on with Contact Cement) and bobs your uncle.
To get better SQ, sound deaden the panel & door card.

Slap the tweeters in the factory 4" position, or into the door card as well. Have Faith in Yourself and cut up the door trims

Removing Door Card:
1. Get a window winder removal tool from Repco to take the winder handle off. The tool is a big fork that pushes out the handle retaining circlip.
2. Undo the 2 screws inside the door handle (it doesn't come off BTW)
3. Remove the 3 screws at the front of the door
4. Remove the 2 screws in the back of the trim
5. Remove the screw hidden under the cap where the door handle is
6. Pop the cap out of the door release handle, remove the screw. Slide the handle forward (towards front of car) 7mm, then pull it out and un-clip the release rod.
7. Remove the "door open" lamp if the car has one (it was an option)
8. Grab the bottom of the door trim on one corner and pop the corner out, work you way around until all the edges are loose
9. Lift the door card up and with a bit of jiggling and force the clips holding it to the top of the door come loose.

Voila, door card is removed.

Installation is the reverse of removal.
When you put the window winder handle back on snap the circlip back onto it then position it on the little drive thingy where you want and give it a solid whack. It'll snap back on and there's no messing around with the circlip.

Rear Speakers:
The 6"x9"s fit straight into the factory rear shelf locations, remove the plates and there's a 6"x9" hole waiting for you to drop the speaker into. Too easy. You'll need an angle driver to do the screws tho, its cramped under the rear window.

Indash Speaker:
OEM are shallow 4" AWA's. Megavox makes a shallow 4" replacement to suit.
A deep 4" can be fitted by removing the speakers and cutting the plastic shelf underneath them. Be careful in there, there's some razor sharp edges plus if you hack too deeply you'll slice open the A/C vents.

Removal is as easy as gently levering from the front of the grill with a thin flat screw driver.

OEM Wiring Harness:
Executive came with front speakers only. SE & Elite came with the Premium Sound package, IE. rear 6"s & an EQ in the Elite.
Front only model = 1 plug
Front & rear models = 2 plugs

Rewiring:
Run your own earth, permanant 12V and speaker cables.. only use the factory switched 12v. The stock cables (apart from the trigger) dont carry enough juice for a serious HU.. they have enough trouble with the factory tapedeck (or CD if you're that lucky).

Removing the Console & Headunit:
Slide both front seats as far forward as possible.
At the back of the console is a screw on either side. They were covered by the seat. Remove them.
Open the console, lift the carpet, check there's no retaining screws inside. if there are, remove them
Lift the ash tray out. Remove the two screws. The center console will now lift out. Remember to disconnect the ashtray lamp wire when taking out the console.

Put the gear stick into 2nd (manual or auto, doesnt matter). There are two screws at the back of the gearshift surround that were covered by the console. Remove them. The surround will now lift out. Make sure you remove the plugs for the controls while your at it.

Same as before.. a pair of screws have been revealed. Remove them and lift the facia up and out from the bottom. The entire thing will come out exposing the HU.

Remove the 4 screws holding the factory deck in. Remove the deck. Remove the mounting plates from the factory deck, remove the factory plugs.

Attach the mount plates to the side of the new HU. You'll only be able to use 1 hole on each plate. Use the front hole on the plate, and screw it to the front middle "N" hole on the new HU on both sides.

Wire it all up and then reverse these steps to re-assemble. Test the HU before assembling, its a pain to pull apart 3 or 4 times in one day.

One suggested improvement to the passage quoted above.......

Instead of just using 1 hole in the mount plates on each side, you can drill an additional hole in each mount plate to align with the appropriate mounting holes in the new HU. This way, your new HU will be held in place by 2 screws each side minimising it's ability to move.

Otherwise a great tutorial. Very helpful.

Cheers

Pete

After just doing my TR Magna this past weekend, I can add a few more notes.

* If you pull up the carpet a touch on the left of drivers side (near/behind the right side of the center console/dash), you can see a rather large grommet. I managed to get 1x 2AWG cable and 2x 8AWG cable through it with a bit of screwdriver poking
* The grommet between the car and the door (not sure if there is one if you have no central locking or power windows) is attached to a clip on the car side, simple use a flat head screwdriver to unclip it and pass your speaker wires through in both directions. Unfortunately the door side of mine has come free and I cant manage to get it back on yet
* If you remove the back seat, you can pass wires easily up through a white plastic thingy and then to the boot. I fit the 2 gauge power cable on one side and 3x RCA's on the other. And speaker wire etc.
* If you want to mount your tweeters in the dash, getting speaker wire through on the drivers side is quite a pain (so is the passenger, but driver side is worse). I just taped the speaker wire to a coathanger, poked it up through the little hole and used pliers to grab the wire.
* Getting the factory 4's out can be a pain (worse on the drivers side).. took me quite a while but I managed with a pair of pliers and just a screwdriver bit. But then I have quite small hands I first tried to use a ratchet with the screwdriver bit, but alas, there wasnt even enough clearance for that under the windscreen.

Bout it. Cheers to Blackice for this tutorial plus all the help he gave me by email.