The Aspen White limited edition is rare indeed. How many miles does it have on it? You might want to keep the Sub because Subaru is well known to have pretty horrible stock sound systems. As for the exhaust it may just be a cat back from an STI, but I am pretty sure that they would sound the same since the diameter is the same, 2.5 inches. I would take it to an Subaru dealership and have a technician check it out so you do not have any surprises after you but it. Good luck.