Just picked up a '95 Legacy wagon, Automatic, AWD. The car seems to run and drive fine, but the rear tire don't seem to have power. Where should I begin?

How have you determined that the rear wheels don't get power?

Remember, this is AWD, and not 4WD, so the wheels are not all 'locked' together (in other words, you can spin the front and back tires at different speeds).

With the Subaru AWD and auto tranny, it splits the torque 90/10 to the front/back tires. Once the computer detects slip, and then it will vary that up to about 50/50 torque split

If you put the shifter into reverse, or the 2 position, then the car will keep the torque split at 50/50
Whenever Im having some AWD fun, I put it into 2nd and I can feel the rear end step out when I stop on the gas