Thanks. There was a topic here just about this recently, someone was asking how to power the risers and the cards with 2+ PSUs the right way. As I understand it, it doesn't matter with the usb risers (it did matter only with the old ribbon ones)? So we can power the riser with one PSU and the card that goes in that riser with another? Or is using the same PSU for both the riser and the gpu is still better even with usb risers?
The issue is tying the 12V lines from 2 PSUs together. With server PSUs its usually no problem as they are designed to load share, but not for most ATX PSUs. Even the ribbon risers are OK to power separately if you cut the 12V lines.