Most people use the 4-pin psu to 6-pin pci-e adapter.
Your power supply has enough amps.
I don't see any problems.
500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for ATI CrossFireX™ technology in dual mode)
Certified power supplies are recommended. Refer to http://ati.amd.com/certifiedPSU for a list of Certified products
This should be fine:
The graphic card I am buying uses 2x 6pins and going to overclock to max using ATI overdrive. By the way, I need at least 2x 6pins and this PSU 132563 is too expensive. 8pins is essential for faster graphic card on the future but I don't need it yet.