Not sure, I really think all the Nvidia cards will work on 460 power supply. I got mine because the power wattage was I think 65 watts, that way I was assured my 460 power supply would work, make sure you have a PCI-e connector, I had one on the ATI 5770 hd, so it worked out good.
Dell is going to hurt on this free upgrade to windows 10 for not supporting the XPS 8300 any longer. No one is going to depend on Dell to supply them with drivers if the windows changes again.
Dell should have sent e-mails out to everyone with the XPS 8300 and at least advise the user of what needed to be done to the XPS 8300 to run windows 10. I guessed at mine, because my resolution was flickering sometimes, that the driver was the problem with the AIT/AMD 5770 HD card. AMD didn't have good drivers for the also, Dell should have told us that. I took a chance and got the Nvidia 750-ti, luckily it worked with the 2-gig card, it has DDR 5 memory.
The next time I upgrade my PC, I'm going to have it done locally, and not with Dell, I can't depend on them any more. I always had Dell, not any more.