I have a non Turbo 2.5 2004 Forester EJ251
Yours has EJ253. I think it is very similar
Oil Filter is $5 - 6 Bucks (Napa Gold/Wix Filter)
Engine Oil is anything 5W30
Super Coolant is $20 per 4 liter
I forgot how much is Fuel Filter , PCV Valve and Spark Plug but it is at par with my 1990 honda accord.
This is my first Subaru , I can't say for sure. But so far I am very surprise to learn that most of the parts are pretty affordable.
2005 Legacy uses the same Fram Oil Filter model #3593 as 1990 honda Accord I Think
I Learn a lot about general info on subaru from this website
http://www.cars101.com/subaru/legacy/legacy2005.html