Welcome to the forum!!
All the detectors you posted there are good detectors, except for use in wet beach sand conditions. VLF machines just don't do well in salt water or mineralised conditions, no matter what anyone tells you.
I would also not worry about iron audio on your detector. I had an Ace 250 for a few years, and I never needed that feature. Even with owning an ATPro now, I still very rarely use the feature. You can use any of these detectors in water, as long as the control box doesn't get wet. The coil is waterproof.
The problem with buying detectors online, and not from a dealer in SA, is that there is no warranty and no support if you ever need it. In my mind, that would make buying local a better idea. There are several stockists around the country, Henry Clapton being one of them that actually lives in PE if I am not mistaken. I would contact him and pick his brains. He will offer you a good deal.
So....which detector should you buy?? That is going to be up to you, but don't buy any of the ones you listed if your heart is set on wet beach detecting. Otherwise all of them will be perfect for what you are looking for.