Hohner - Sextet Harmonica KEYS C, G, Bb, F, A, D - 2kg

If the double-sided Echo does not offer you enough variety, you could consider the Tremolo Sextet or it's German name, Kreuzwender which is, as its name implies, six tremolo harmonicas in different keys mounted on a central spindle. The keys included are C, G, B, F, A and D. Replacement modules in all these keys (and also E or C minor) are available singly should you wear out the one you use most.