CS5 Photoshop/ GPU?

[cu3ed]

Just a curiosity more than anything, but how good a GPU do you need to get the most out of the likes of photoshop CS5 with pretty large graphics and plenty of layers?

Ive noticed it stuttering a little or "pausing" when using the transformation tool for some graphic work, I have 8GB of RAM, win 64 CS5 64bit, but the graphics card isnt brilliant.

 

[cu3ed]

Cheers, I have sitting here an Ati 6570 to install as the weakest thing at the mo was the current card (cant remember its name), so will give that a bash.

It was more a curiosity than anything.