A live box covering their entire career with DVD of the central park concert that was on HBO and footage of the July 4th Washington DC concerts. 6 CD's should do it, including Chicago, Lei'd in Hawaii, Wild Honey 67 tour, Big Sur, Carnegie, outtakes from Live in London and In Concert, Paramount box set tour, etc.
Don't forget the 1978 Australian tour! Carl's vocals sounded very honest on that tour.