If your going to live in Hawaii why don't you hunt where the majority of the silver, gold and platinum jewelry is found......In the wet sand and in the water.
If i was moving to Hawaii and wanting to metal detect the beaches there I would be in the water, I beach hunt here in Florida, there is 100 times more jewelry found in the wet sand (from people playing and swimming at high tides) and in the water then in the dry sand, there is a 100 times more trash in the dry sand then in the wet sand and water........
Forget the ones you listed, get a good water detector, a Excalibur 1000, Whites Dual Field or other PI unit, Whites Beach Hunter 300 and go in the water where most of the jewelry is found.
If you are 100% positive you will never go in the water, get a Sovereign GT and put a Coiltek 15 inch Coil on it. You will not find a better beach wet sand / dry sand machine then the Sovereign GT, and when you add the WOT coil you will have a beach vaccum. The Sovereign is the land version of the Excal......
Remember wet sand use to be under water at high tide, only place you will find more jewelry then in wet sand is in the water. You want a machine that can handle the salt water mineralization....None of those listed can handle the salt water mineralization like you need. It is like going dove hunting with a 22, it will work but not well. If your going dove hunting take a shoot gun, if your going beach hunting in Hawaii take a water machine. If you want to compete, you need a water machine to compete with.