Big thanks to Nate (Skyline8409), almost all the goodies are now installed — COBB Springs and sway bars and SPT exhaust. Difference is immediately noticed at first drive. Car is way more responsive on cornering as well as it is stiffer. SPT catback gives fake feeling of more power :). Despite that Nate owns an '06 STi, he was pleasantly surprised by the car. He says it's lacking immediate torque but other than that he likes it. All in all I am very happy. I am still getting used to it. Front springs might be slightly too low as I can hear strange bumping sounds. But it's consistent on both left and right side. So I am assuming it's normal. I will however double-check everything.