You should remove the 5V and 3.3V regulators before using an ATX supply. The problem is that you will create loops between the regulators on the hub and the ones in the ATX supply. They may fight with each other, waste power, and get hot. You could just plug in the ATX supply with the regulators in place and see what happens. It worked out ok for Jim but there is no 3.3V regulator on the passive hub so there is a bit of a difference. If you do, keep an eye on the regulators and make sure that they are not getting hot and if so, remove them.