I need a replacement for the Nvidia 220 GT

I have a Dell Studio XPS 8100, and I need a replacement for the Nvidia GeForce 220 GT that came with it from Dell, simply because I want a bit more FPS in my games. But I'm limited by my PSU, which is a Chicony cpb09-001b. I was looking at the Sapphire Radeon HD 7750, but it has a requirement of 400w, my PSU is 350w. I did some digging around and used Newegg's PSU Calculator, which tells me that the wattage with my loadout and the 7750 is 343w, and the wattage with my current 220 GT is 345, which means that if I get the 7750 it'll be using LESS power, and it will be able to handle the new graphics card easily. Is this correct?