> To my knowledge it was just that one 2.5 liter 4 cyl that had HG issues.

Yes, it was primarily an EJ253 issue (they used shitty gaskets, the design itself was fine), but Subaru put that engine in every car they sold for quite a few years. That being said, you just roll the head gasket replacement into the timing belt service and it's not the end of the world. I had an '06 Impreza wagon for years and it was a great car.