Re: xps 730 & gtx 480
You should have 4 6-pin PCIe power cables. The 6-pin to 8-pin adapters should work as long as they have 3 yellow wires and the cables on your power supply have 3 yellow wires. The power supply should sense the 8-pin being plugged in and provide enough power through the 6-pin since it can provide more than 75 watts. I would initially just buy one GTX 480 for the $200 cost versus buying two of them and one of the adapters to see if it works properly. You may be happy with your gaming with just one anyway versus your current set up. If everything is working correctly and you feel you need to run them in SLI, then buy another. They are the same cost on Newegg also HERE. I do see though that they are providing the adapter to convert two of your 6-pins to an 8-pin which is probably the safest way. However, this would not work running two cards in SLI because you would then need six 6-pin PCIe power cables and you only have four.