You're the real one for putting the actual part numbers for the adapters here, regardless if they work at least I have an idea! Sorry for bumping an old threadI just happened to be looking into this exact same question. I have an Australian Outback 2005 2.5i.
Took the panels and speakers off and made some templates of the holes. The front has holes at 0, 130 and -130 degrees at a radius of about 88mm. The rear has holes at 0, 130, -130 degrees at a radius of about 92mm. So if you start with a front speaker adaptor and extend the holes radially by 4mm it should fit pretty well. Note: I haven’t actually done this so there could be some unexpected issue doing it this way.
So, whilst IA Tuning say their adaptors would fit both front and rear, I can’t see how that can be the case (unless you modify as per the 4mm radial adjustment above). If you order two IA Tuning kits it would cost US$44 plus shipping (cost?). If you buy the custom made PVC ones it costs US$76 including shipping.
When I checked the MJM vehicle checker, it said the SAK032 wouldn’t fit an Outback/Legacy, so not sure if I did something differently. SAK065 do apparently fit the front, but no rear solution (unless you modify as above). Car-speaker-adapters.com would cost about US$80 for two kits.
What about tweeters? Has anyone found either a tweeter that fits the existing bracket (35mm diameter), or a supplier of brackets?
What about speaker plugs? Reading a few different posts, think the right ones are Metra 72-8104 for the front and 72-9300 for the rear, be good to have this confirmed by someone who has done the speaker upgrades.