hey seymourless,
i have a 2005 legacy gt 5eat, i once thought there were no aux options up until last year when i came across this:
theres an iphone version too. but this thing is awesome, sound quality is superb for bluetooth streaming and its relatively cheap to install. actually is hardwired in to the radio so its not like that crappy standard fm transmitter from bestbuy. you need an antenna adapter as well but i got everything done at a local audio shop (jo dis in CT) for around 150 for the transmitter, adapter and install. totally worth it! just thought you should know. also, it doesnt require any taking apart of the radio unit itself like that silent cd mod r w/e does, so you can always remove it. theres a wired version as well that can use any standard headphone jack