Middle of last year I bought a NZ new 2006 facelift Spec B legacy 3.0 wagon 5EAT with 139,000km from Whangarei. The 3.0's are rated to tow 1800kgs ( 2.5 is 1600kg ), and I've towed about 1650 on it so far, and it goes very well. Around town the trip computer says I'm using about 10.8l/100km, and I was concerned that would blow right out when towing, but to my surprise it stay exactly the same. Then again I'm towing down the motorway to Hampton Downs so no stop start and hills and crap. My car is not tuned, it's completely as it left the factory ( ok I changed the oil and it's had a set of tyres ), and the paddles are great for knocking it back a gear up the hills. Easy cruising, easy towing, still got a very nice daily driver, I love it and couldn't be happier with it.
Make sure the towbar rating matches the cars' towing rating ( on any car, not just Subaru ). I looked at a 3.0 legacy wagon that had a towbar, but it was the 2.5 towbar, so only rated to 1600kg, not 1800. Walked away from that one.