Hello everyone, Since i bought my 02 Wrx i've been wanting to upgrade my stereo. Since I couldn't find any really indepth guides, I figured i'd write one for the forum thats up to date. First you're going to need to need to decide what you want and need, also you're budget. I picked up a JVC KW-AV60BT 6.1 off ebay for 260 bucks with free shipping, and a wiring harness like this. *NEW* SU-8900 SUBARU 1993-UP POW/SPEAK RADIO WIRE HARNESS METRA 70-8901 | eBay
There are two ways of connecting the wires. First you can use Butt splices, which just crimp the wires together for a pretty decent connection, all you'll need is some pliers and electrical strippers. You can buy them anywhere from lowes to advance auto parts. You won't get as good of a connection as if you would of soldered them together, thats the method I used and going to walk you through.
Once you have decided on which way you're going to go, and I will strongly suggest you solder the connections, open up your stereo and get out the power supply that plugs in the back of the system. Get the wiring harness you bought for your car and set them next to each other. You may have a few wires you won't use if you car doesn't have features like controller buttons on the steering wheel, or power antenna. Read on each wire what it does, and compare to the color coded harness that goes in the back of your stereo. Just match colors, and colors with stripes and you'll be all good.
Please note, i'm going back and showing you how to take out the stock unit. The pictures are from where I've already installed everything, but it's all the same. I didn't feel like putting the stock stereo back in just for pictures. If you have any questions, feel free to ask and i'll do my best to help you out.