[...]as stated both ati and nvidia are working on photoshop support which isnt yet released any when is will probably require a new gpu.
It is not ATI and nVidia that are working on Photoshop support, but rather Adobe working on GPU support.
Thus when the functionality is available, it is highly unlikely that it will require a new GPU- to explain it simply, Adobe just needs to make use of pre-existing possibilities already built in the modern graphic cards; it is not the manufacturers who need to add further functionalities.
(and to explain it technically, what Adobe is doing is rewriting the image treatment code to GPU language (most probably HLSL but they could use GLSL as well) instead of basic x86 code)
Just wanted to point that out.
Otherwise for the hard drive, it is up to your personal choice really, but I wouldn't recommend having a 1 Tb hard drive, but rather two 500 Gb ones. The price will be mostly the same, but the thing is that when a drive fails, you'll still have another one. Whereas if you only have one, you'll lose everything.
It is definitely not a question of speed, which will be the same in either case, but of reliability.