I'll add pictures when I redo everything again next month to add Dyna-Mat. The installation is very simple.
You'll need a Trim Panel Removal Kit to follow this guide.
Note: Amazon and other websites may say that certain parts I link do not fit the Mirage. This is because the Mirage is new, though it's possible with time that better, closer fit, parts will come out. However, every part I've linked I am personally using on my 2014 Mitsubishi Mirage DE (USA) that I purchased the last week of December 2013.
First things first, you'll need a double DIN head unit and a wiring harness.
Connect the wires to the harness that came with your radio, following your radios guide. Do not just twist the wires together, either use crimped connectors or solder them. They will come apart eventually if you don't. If you want to use an amp, don't connect the speaker wires to the head unit.
I'm assuming you have this stereo:
If you do, you need these parts from your local Mitsu dealer (around $90 total, remember to say "Can you do anything with that price?", they'll usually knock 10% off):
Front Panel: 8002B480XA
Brackets: 8750A262, 8750A263
If you have the nav installed you already have these parts and don't need them. I don't have the nav unit to test on, but to remove that it you should probably pry from the bottom of the trim, once you can get your fingers under it pull up, do this for each side. It should just pop off.
The trim panels need to be removed by starting at the top and working your way down. Using your hand, try to grab the edge of the vent and lift, while doing that slide the panel removal tool (the one without the forks) under the panel. Pry the panel up. Once you can get your fingers under it you should be able to pull it off. It will offer resistance and won't just pop off like nothing. Once that is off disconnect the hazard light switch cable harness and set it aside.
Remove the 2 visible screws at the top and place them in the cup holder, navigation units have 4 screws. Once the screws are out, pull the unit out. It has some clips and will offer some resistance. Once out, disconnect all the wiring harnesses from the back of the unit and set it aside.
Attach the brackets you purchased to your new head unit. If you have a nav unit, remove the brackets it used and attach those to your new head unit. The brackets used on the standard (non-nav) radio do not work with nav-style head units.
If you are also installing an amplifier you should install those wires now.
Attach your wiring harness adapter to the factory connection. Reconnect the wires to your new head unit. There will be a few left over, one of these is for the USB cable, the other I'm not sure about but it doesn't seem needed.
Replace the head unit into the dash, being sure that no cables are pinched. Put the screws back in. Those that had the nav unit previously can now reconnect the hazard light switch and replace the front trim panel. You're done!
For those using the standard (non-nav) radio, remove the vents from the top trim panel. They snap out and come off from behind. Snap them into the new trim panel. The switch for the hazard lights releases in the back and comes out the front. Pop it into the new trim panel. Once that's done, put your new trim panel on. You're done!
It should now look like this:
You'll need 6 1/2" speakers, wiring harnesses, and speaker adapters. Note: You WILL be drilling new holes to install the speakers.
All 4 doors are very similar, the front doors have an extra trim panel that needs to be removed. I just pulled this off by hand, but you can use one of the panel tools. The front doors have 1 screw on the edge and the rear doors have 2 screws on the edges. Remove these. Remove the screw in the door pull cup (where you grab the door to close it), pull up on the trim piece and slide your trim removal tool under it and pop it off. This reveals 2 screws, remove them. Finally, remove the screw by the door release handle.
Starting at the bottom of the door slide the removal tool underneath, there is a slot underneath for this purpose. Pull up until you can get your hand underneath and pull outwards. They offered a LOT of resistance when I did this and it took several hard tugs to release it. Once it first pops off it's easy to pop the rest off. Slide the door panel up and away. Disconnect the wiring harnesses. There are blue and yellow colored cables. Remove the yellow and blue cables by pulling up on the colored plastic, rotate them and slide them out.
Once the door panel is off, disconnect the wiring harness from the speaker. Turn the speaker counter-clockwise to remove it. Hold the new bracket over the hole and using a drill put in 3 self tapping screws. Connect the wiring harness to the OEM connector then to the speaker. Install the speakers into the bracket. Test the speaker for functionality.
Reverse all the steps to reinstall the door panel. Tip: If you forget which of the colored cables goes where, use the power door locks and watch which cable moves, that's the one that goes in the top.
If you only have one amplifier I highly suggestion using the passenger side. While it's farther from the battery there is more room under the seat and the trim panels on that side have routing paths for cables that are not being used. I was unable to find a pre-drilled hole so I fed my cable through the fender and in through the door, you may want to drill to install it. It's up to you.
In addition to that I highly suggest upgrading your electrical system, it will also make installation easier. You should pick up a new battery, along with a dual terminal kit for it. That will give you 2 battery posts instead of 1, making installation a breeze. You need the battery I linked to install the dual terminal kit I linked.
All door frame trim pieces can be removed by hand. Remove the one in the center first. The panel with the seat belt requires removing the back seats. Simply pull up on them and they come out easily. They are actually made for easy removal. Remove the large black trim panel and then the seat belt area trim panel should remove easily. Start from the back and get it over the metal. Once it starts coming off it removes easily. You'll be able to see a clear pathway for cables at this point.
I routed the RCA cables down the right of the center console and the speaker cables up the left, but my 4 channel amp was on the drivers side because I had a sub amp on the passenger side. I used the seat bolt on the doors side as a ground, this seems to work.
Wire up everything and reinstall it all. Don't forget your fuses!
You can see my setup here. I have a kicker 500W 4 channel amp (75W*4@4OHM) with a 1200W (800W@2OHM) sub amp powering 2 12" subs.
When I was doing research for this, I had someone at Best Buy and 2 people from a local shop tell me it was impossible to put that much power into a Mirage. With my upgrades I maintain 14V easily with the car idling w/the high beams on. I have a capacitor but I did not install it yet, I want to see how it preforms without it first. So far it all seems fine, but it's only been a day.