installed an ATI Radeon HD 4870 in my XPS 9000 with no problem. Dont know what the equivalent is for the GTX but it might give you an Idea. The power supply for the XPS 9000 says 475 but I've read that it can take a stronger load. Only problem I had was finding the two power cables, dell hides them pretty good look for black and yellow wires. I
I installed a GTX 460 (factory overclocked to 725MHz) in my XPS9000 and had no issue whatsoever. I believe the stock PSU is actually rated to 525W and might be able to handle a GTX 570. And I others on this forum have upgraded to the new HD6950 or HD6970 and had no problem either.