What should I take for a trip to South Italy?

You know what you like about your gear better than us. What would you take if you were ushering visitors  through your home city of Hong Kong? That would be what you need in Italy,

If not buying new gear, I would take the EP3 with 9-18 in a small bag with 25 and 45. Put the 14-150 on the GX1 as your main camera.

If switching to OMD, use that with the 12-50. It's more than  fast enough for tourist pics. Carry one of other cameras with the 9-18 in a bag.  Bring 25/45. Pick up the 40-150 zoom if it's bundled cheap with the OMD. You won't use it, but who knows.

If you go to Capri, walk up the hill into the town and find an outdoor cafe that overlooks the harbor. Relax and forget about sightseeing for a while.  At the same time, don't miss the crazy Blue Grotto water tour, which was the funniest money grubbing performance I've ever seen by a guide. "You no tip me, I tip  boat, no?"