Exactly, so let's say you have one epic spawner, and if you have other 100 normal spawner, you can upgrade the lvl1 epic spawner to lvl2 epic spawner. Now, to be honest I've never tried to upgrade or prestige spawner, so I don't know exactly the process, but from what I know if you right click on the placed spawner, there will be a GUI pop up and in there you can upgrade or prestige the spawner too.
If there's anything wrong from what I said, please let me know. Thanks