The car in question is a 1991 Legacy wagon, 2.2 automatic. It's coming up on 225,000 miles, G*d bless it.

The radiator is leaking, and I'm going to replace it. I figure that I'll replace the upper and lower hoses while I'm at it. As long as I have it apart, is there anything else that I should replace?

I'm thinking of cooling system components specifically, like the thermostat or the water pump, but I'm open to other suggestions. I'm also open to the suggestion that I just leave everything else alone. My inclination to replace stuff "while I'm in there" is probably caused by my experience in the world of Audi, where it's SOP to replace the engine every time you change your radio station presets.

We haven't had the car that long, and I'm not altogether familiar with its maintenance history. In my experience, cars don't get to have 200,000 miles on them without being maintained, so proper maintenance is probably a safe assumption.

Thanks much.

There isn't that much you'd do just because the radiator was out, perhaps the thermostat as you mentioned.
Has the timing belt been replaced? If not this might be a good time to do it, since having the radiator out does make the job easier. The water pump is under the timing cover and driven by the timing belt, so it normally gets replaced at the same time as the belt.

I'm usually a little skittish about replacing a working thermostat. I've experienced two that were bad out of the box, which necessitates taking the whole mess apart again. I guess I could boil the new one beforehand and check it.

I'll take a peek at the timing belt while I'm in there. I doubt I'll replace it if it looks good, though. The kit is ~$300, which is almost as much as I paid for the car. (I'm assuming that you replace the tensioner and the idler pulley with the belt, rather than just the belt - is that correct?) Given that it's a non-interference engine, and that I have spare cars, and that the Subaru rarely travels more than ten miles from home, I'd rather just wait for it to fail and take care of it then. I've read the procedure for replacing it, and it looks dead simple (especially in comparison to the last one I did, on an A4 - "Step One - Unbolt everything from the fenders forward...")

Thanks for the advice, Your Moderatorship :)

I only mentioned the thermostat because you did, it certainly isn't necessary to change it if it is working properly. It's only a little more convenient to do so at the same time as the radiator because the system is being drained anyway.
As for the belt it's up to you, but unless you have the maintenance records for the car (which you apparently don't), it's not a safe assumption that the belt was replaced recently. It most likely has been changed at least once or twice in the car's life given the mileage, but the last time could have been a while ago and possibly longer than the recommended interval. At the very least pull the cover and inspect the belt very closely, be sure it is tight and there are no cracks or missing teeth. Look at the base of the teeth as they sometimes begin cracking there.
Replacement of the tensioner and pulleys isn't required but is recommended at the same time as is the water pump, this is just to avoid any problems later on and because you wouldn't want to perform the same labor all over again should one of those parts fail.

Thanks, Mulder, I appreciate it.