Don't forget Cafayate in addition to all other Salta-region visits already mentioned. Salta is awesome!! Then in Bolivia you'll want Tupiza-Sucre-Uyuni (or start in Sucre then backtrack to Tupiza to do a 1-way trip through the complete Uyuni salt flat tour and end up in Uyuni where you can take a bus - pick the fanciest one! to La Paz). Then from La Paz get a flight package to Rurrenabaque for a Pampas tour if you like the jungle, and if the season is right. Otherwise you have similar jungle visits in northern Peru. Don't miss Copacabana Bolivia (+ day trip or overnight stay on Isla del Sol - again, if the season is right) and then Machu Picchu of course.... Lima is the furthest I've got but I have some recs from friends on Ecuador and Colombia, if u want them just private message me and i'll give you the info I've gotten from people who have been there!! And for Colombia-Panama why not make the connection via a tour of the San Blas Islands!!!