if you're going to pull the engine anyway and if it has at least 100k mi, maybe do the head gaskets too for good measure. certainly if you have 150k mi and they haven't been done before. it would be bad to be enjoying your new clutch and soon after have to pull the motor again.
BTW do you or others know if there is an improved Subaru or aftermarket clutch design? I owned 2 different '00s and the clutch shudder was bad at times. It was unpredictable and always did it from the time I got them at about 85 to 100k mi. I didn't keep them long enough to really figure that out, though. (First one wife totaled, second traded for '04).