Am I right in assuming that any culture that has abundant and cheap fusion power would be able to produce unlimited elements? Hydrogen fuses into Helium at about 100 million degrees. Helium fuses into Lithium, Lithium into Beryllium, Beryllium into Boron, and so on down the periodic table. If you can fuse one element, you should be able to create any element with a bit of technological tweaking. All of the elements in the solar system were created by a big fusion ball - the sun. Or it's predecessor. So all you really need from the Kuiper Objects is Hydrogen (i.e. ice before it's refined). If you get a powerful enough fusion plant - you're about a half a step away from the replicators on Star Trek. Once you can create an element - the next step is putting different elements together to make a compound. Once you can make a compound - you can make food, clothes, machinery, etc... Granted, it may take time to figure out the patterns, but the basic technology is there at the beginning of the fusion age. To me, I would think there would be stations around every Gas Giant to pull this abundant resource - hydrogen - to be able to create other, more rare, elements.
Scout