Hi I have just fitted new head unit a one Din Kenwood KDCW 6537U £120 with all the cables for I-pod and adaptor for Subaru
Plus a one Din pocket from a Forester £19 from Subaru (just right for the I-pod)
I am into sound and my speakers in my 06 are fine for a car
So I would change just the head unit first then if you do not like the sound go for new speakers.