xps 730 & gtx 480

No i would not recommend splitting any of the connectors you need an individual connector. Strange that it only has 3 connectors I believe that there should be 4. but at the moment I cannot find a diagram of your powersupply layout

Thank you so much for the help Davet50. But do you think i should use two of the 6 pin connectors from the ps with a 6 pin to 8 pin adapter & have each one going to the 8 pin connector on the 480's & then split the remaining 6 pin connector from the ps with a 6 pin y adapter to go to the remaining 6 pin connector on each 480.  Thanks again for the reply

ok i will open my case and check & if there are 4 i will use all 4. i could be wrong but by looking at the specs on the ps there are 5 12v rails so i'll check

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. 

hi again

well i read the owners manual on my xps & i doo have 4 6 pin connectors so instead of getting the 480's i think i will go with either the 470's or if i can afford it 2 570's as both are dual 6 pin connectors

I had 470's in my 720 and they performed well. I have  the 570's in sli in my home build and they scream, and draw nominal power.  I would recommend that if you do go the dual route that you get a free fan control program such as MSI after burner to run custom fan controls as they do have a tendency to run a tad on the hot side without it. 

The GTX 570 is a better performer over the GTX 480 and can be found cheaper now than the older GTX 470 they have replaced since there is a smaller supply of 470s unless you buy them used.  

thanks davet50, i will do that but won't the nvidia control panel regulate the fans or is msi afterburner a better choice ?

I like the MSI afterburner as you can alter the stock fan pattern.  The stock will do a adequate job but setting custom profiles can be a bit intimidating. Afterburner is a lot easier to setup