I've recently acquired an E-P3 with 17mm f2.8 and will be adding a prime or two but would like to add a walkaround zoom. The options seem to be: 1. 14 - 42 mm II 'R' (Cheap option.) 2. 12-50mm (Middle option.) 3. 14-150mm (Costly option.) I understand the differences in spec and capability but is one of these lenses significantly better optically? I've only really considered Olympus, is there a Pana option I should go for? Many thanks in advance for your advice and opinions.