I have bought a few Boxsters, most of them on the depreciated end of the scale. What I have seen is that the raw statistics of age, miles, and equipment don't always tell the story of which is a better car. If they are local, try them all out before you commit. For me the feel of the ride, smell of the leather, and sound of the engine makes one of my '99s stand out as a favorite. It can be hard to quantify.
I drove both a base and S today, same smile as I drove them.
For cost/expense, little things can add up quickly. Replacing old tires can add $1,000 to the cost if you go with a premium performance tire. If any of those cars have an original (or in my opinion over 5 year old) water pump, it should be replaced immediately - Up to $300 DIY or ~$1k at a dealership. Consider those type of expenses when you have your PPI.
They all look like good prospects. If I was considering the 02S with 52k, the value of the hard top would be a good plus, but the maintenance falls a bit short of what I'd like. Many owners who don't frequent the forums don't care about replacing the IMS. If it is a big concern for you discuss it with the seller and see if you can get by with a lower offer.
Enjoy the search