Unfortunately the PCIe Slot power is at least 5Amps or so for the 470/480. Some of the 6 pin 480 even use much more than 5 Amps. You can't power too many of them with the daisy chain Molex and especially the SATA connectors. Even the 8 pin 470s draw around 5 Amps from the slot.
If you have the space, best would be to install NO MORE THAN 1 of your 470/480 directly onto the motherboard.
I would avoid using any SATA connectors to power any of the 470/480 GPUs. They draw at least 60 watts and those SATA connectors are generally used for hard drives which draw about 5 watts on average.
I wouldn't use any more than 1 of the Molex connectors to power any 470/480. Usually a PSU has 2 sets of these (6 molex in total) so you can power 2 GPUS from each seperate chain.
The best method would be as follows. Usually most PSUs have 2x 6+2pin on each chain such as follows.
You would plug in one of those to your 470/480 #1
connection and the other would always be unused. Since the length wouldn't reach the next card. So you would buy a PCIe extension cable such as below
Plug in the unused PCIe #2
connector to this extension and splice the other end +12V and GND directly onto your Risers power.
This way you could run any number of high power 480s and overclock them to the max and you would never have any melt since the PCIe has plenty of power and is a higher gauge.