Sorry for the late reply, I am a big subaru guy and have owned tons. You are spot on with your analysis. I have had 3 STis and a ONE WRX
I ordered a 2016 STi new in what was (back then) considered the purest spec. Zero options except for the performance exhaust upgrade. I passed on the short shift kit because the standard STI trans was great and I didn't trust the port to correctly install it after seeing a friend who had a WRX months prior have port installed options fail.
That was my first. I only had driven old (stock) Mitsubishi Evo's prior so during my time with the STi......well let's just say I was disappointed being I waited my whole life to get the STi....and I knew something was off
Fast Forward a few years later I got an 05 All stock besides a day 1 installed HKS catalogue exhaust (Catback) and my 2016 STi I bought new was gone. I got the 05 dropped off on a Sunday evening and by Friday at 9am the 2016 was traded in. Not even kidding...it's that big of a difference. Additionally Data readings a track rat friend took for me out of my own curiosity (I don't beat my cars) found the 05 to be substantially faster in all high way and low gear acceleration testing.
I could write a book, but I am one of the more knowledgeable people regarding these STis - to the point where some of the newer US Subaru corp management contact me with questions and inquiries on my thoughts - on a fairly regular basis. We have met at some of the big Subaru shows and remained friendly since.
In Late 2007 Subaru gave the contract to a new piston supplier....so the reliability and ringland punching bag jokes the car world throws on Subaru's is near 100% due to that. Most 08s to 09s had seriously defective engines. Emissions required changes that started in late 06 and where very bad by 08 MYs caused the engines to become ticking time bombs when modified....anyways
04-07s are the best , and the 05-06s are the pick of the bunch from a performance perspective. They just are true rally cars for the road that do everything you expect them to and are more of a raw drivers car.
Don't ever drive a 03-06 Evo that is stock or well sorted. It will ruin you! They are unbelievable cars.