Well I can say this...I have seen properly maintained Subarus last people over 300,000 miles. With that being said, the decision to keep or sell the car is up to you..Obviously as you mentioned the higher the mileage the more things are going to need to be replaced ( usually ) So If you keep on top of replacing things it will get expensive but you will also have a good running car. Are you the only owner of the car? Describe " the power just isnt the same" Is the car boosting at all? When was the last time you had a full tune up ( 60k mile service)? If you start modding things It can/will get more expensive than a routine service. Did you have the t-belt changed at 105k miles?