Mines an 05 outback so not quite the year or make, but I do find the 2.5N/A a nice compromise between turbo and H6.
Its got enough low torque to be useful when towing, but still economical enough for around town driving.
It gets about 10kms/l for around town/ stop start type traffic (about 8km journey each way to work and about 100kms a week on 80k roads)
On the open road I can get up to 14km/l.
If you can get a late model BP with most of the BM stuff like proximity key and start button, then with the price difference between the BM and the BP you should be able to get the stereo replaced and still come out ahead money wise.
I am not a fan of the BM's as much as the BP style.