If you're playing at 1680 x 1050 resolution or below then there's no real need for a 1 GB version, but if you do it should work, it's going pretty close though (the 512 MB & 1 GB version consume around the same amount of power.)
If you want to play it safe you're better off with an HD 5570.
that graphics card requires 300w i am pretty sure that i only have 250 but am not 100%. at this point i figure i better just go ahead and install the new power supply or i'll end up having to upgrade it anyway when the 512 becomes obsolete in a year or 2. damn blizzard and my love for starcraft
It's recommended a 300 W PSU, but @ legitreviews their test computer (Core i7 975 @ stock) with an HD 5670 only used around 226 W load. You've most likely got a less hungry CPU, but then it's quite risky if your system say consumed 200 W.