Amp for klipsch KG4

I've got a set of KG4's I bought new around 1990. They are in very good shape so I want to put them to use. I retired them quite a while ago and have decided to give them to my grandson. I'm looking for suggestions on an amp that is well matched and affordable. A receiver, or integrated would be fine but if I can find separates that would be best. Since he is only 12 and has active younger brother and sister, solid state is probably best suited for him. Any advice is greatly appreciated!