dell xps 420 gpu/psu upgrade

I'm looking to upgrade my gpu to a GeForce GTX 560 Ti from a Radeon HD 3600 Series card. I know the current 375w psu will not be enough so I was going to upgrade to 600w. Just wondering if this is possible, as I read something about how Dell used to use proprietary motherboards. Thanks in advance any input is appreciated.

Any ATX type PSU can be used, Corsair are a good make HERE, I have the CX500w v2 in my 570 system. Dell do use propietary motherboards, but that will only effect CPU's and system cases.