When I bought my 98 Outback, it was producing a vibration in the 1800-2200 RPM range. After going back and forth to the dealer getting the " It's normal" response, I did some thinking and came up with the engine mounts (isolators) as the most likely problem. Even though the car was still under warranty, I had to fight with the dealership to change out the engine mounts. I even had to tell them that if it didn't fix the problem, I'd pay for it. Finally they did it, and the vibration is gone. They ended up putting on the new style isolators (2001+) which work great.
I hope this helps someone out there because I know how frustrating it is having that engine vibration and getting the " that's normal" reply from the dealer.