XFX 4890 XXX PCI 6pins concern

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:

http://www.ebuyer.com/product/132563

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.

Does these helps?

http://www.ebuyer.com/product/151295

http://www.ebuyer.com/product/133115

^ those are both rubbish. for a PSU with that sort of wattage, you should be looking at the £70-90 range.

Corsair.

I used a 6pin to 2x 6+2 pin cable splitter, works a treat! my psu is CIT-750w 26amp per rail, cost me about £60 from maplin. and that runs my XFX 4890 XXX

Come back when it fails so we can recommend a decent one.