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I really need pins capable of 16 amps
Your house is full of 13 Amp pins. Can you imagine eight of those in one shell??
Clearly you want a "mix" of big pins and small pins. That limits your choices unless you have National Budget.
Yes, the UK 13A pin is generous. US 15A/20A pins are smaller, but also trouble-prone.
Paralleling is dubious. Pins have various contact resistance. One "good" pin can hog MOST of the current. Sometimes the heavy current degrades the contact and it tends to self-equalize. But I have seen parallel contacts who did not get that memo.
A functional and VERY inexpensive alternate is PC motherboard power connectors. You want "extender" (M and F with a foot of wire between; unless it is convenient to have pin-header on your mixer).
TH has an essay on these connectors and ratings. (Skip way down to ATX; you can't get AT-type today).
https://www.tomshardware.co.uk/power-supply-specifications-atx-reference,review-32338-7.html
Today the 24-pin version is more common:
https://www.tomshardware.co.uk/power-supply-specifications-atx-reference,review-32338-8.html
My experience is that cheap ATX connectors have no trouble with 80W 5V (16A) on four pins. They are widely used to ~150W 5V or 3.3V (30+A). I do not know if the "Plus" design is common.
Current rating depends on wire-size... they depend on the wire to draw-out heat.
The
Molex spec says 600 Volts. As a double-shrouded connector it is hard to imagine any trouble at 300V.
Mating is tested (for Molex) to 30 cycles. This is far more than most PCs see. It may be an issue in prototyping or a console which is regularly dismantled and serves several decades.
There is a 4-pin variant used on most modern motherboards as CPU supply (12V to an onboard 1.97V converter). This would surely do your heaters; the other-stuff can use a cheap connector.
https://www.tomshardware.co.uk/power-supply-specifications-atx-reference,review-32338-9.html
I don't have to tell you that 48V 2A is much less copper and contact than 6V 16A, if you can series-string your heaters.