Compression loss is usually due to poorly seating valves. As with the stem seals, it's the exhaust's that wear the most because of the heat that they're subjected to.

If you just have the heads rebuilt, (all gaskets and stem seals replaced and a fresh valve grind/hone), you'd be back to good as new.

Piston rings are the last thing that will cause poor compression, given the beating that the valvetrain gets and the size of the components/sealing materials used.