5A should be sufficient, that is the rating of your existing power supply isn't it? If you have low impedance speakers maybe the 10A would be better when pushed hard but it is really overkill, and there again if you have low impedence speakers you probably don't need to change from 38v to 48v in the first place.Can the fosi v3 use the higher current of the 10a vs 5? Or is it capped at 5a?
Essentially any of those Fosi supplies should work fine - personally I would likely go for the 5A Gaan option as I don't push my amps hard.