Is this powered by 12v or 5v? This is important. Most modern power supplies don't supply any more than 80-120 watts on 5v, even crazy powerful ones like corsair ax1200 or lepa 1600. If this is powered by 12v, that is much better, but still limiting because the hubs requires an atx24 pin connector instead of one of the much more available molex/sata/pci-e connectors.
USB is 5V almost certainly the unit isn't doing 100W+ 12V to 5V conversion so it is powered by the 5V pins on ATX connector.
I have 10 port hubs that come with a 12v @ 5 amp power brick, so I don't think it would be unheard of for such a large hub to downscale 12v to 5v.
Being stuck at 5v input is a shame. Will need to buy multiple ATX power supplies instead of just a single one to run multiple hubs :/