I purchased new speakers front and back locally a couple months back and have yet to install them. I know with our cars we have to deal with clearance issues and a stupid 3 bolt pattern oem bracket. I'm looking into adapter plates and wondering what people recommend. I found http://www.subaruaudio.net/subaru-speaker-spacers/ which looks like a good bet. Front - JL TR650-CSI http://www.crutchfield.com/p_136TR650CS/JL-Audio-TR650-CSi.html?tp=106 Rear - JL TR400-CXI http://www.crutchfield.com/p_136TR400CX/JL-Audio-TR400-CXi.html?tp=102 I know they aren't the best speakers in the world but should be pretty decent.
You should probably return the rears and get 5.25" Speakers. http://www.iaperformance.com/index.php?cPath=44_45_2074_2358_2461 These guys were the first to come out with speaker plates from what I can remember. Actually, that is how they got started in the aftermarket industry. Now they sell pretty much anything.
It's too late to return them. That's why I was looking at the other guy since he does spec to speaker plates
I am currently using his spacers. They are pretty simple and gets the job done. I had an issue with hole alignment on a set of mine and he helped me rectify it over the phone. If that didn't help, he was willing to refund me the money or send new spacers.
i did the front components and i don't remember the install being too hard. i used whatever bracket came with the speaker and had to drill into the door with some self-tapping screws, but that was about the hardest part. everything else mounted right up. i couldn't tell you the sizes (been 7yrs), but the fronts weren't too hard