The I7 and I5 are a "ton" better on paper, but in application, they practically go hand in hand. Especially on something like photoshop, Which I believe only uses 4 physical cores anyways. And for gaming, the Q9400 is plenty enough.
For the GPU, ehh. Get a single GTX 260 Core 216 and call it a day. Pick up an Evga 750i or 780i and some DDR2 DC with the bonus possibility of SLI later. Then get yourself a nice 650 watt PSU - OCZ makes a nice one, so does Corsair. Grab a 7200 drive, Then top it off with a stylish midtower and some case fans.
Unless you intend to get real hardcore, I'd stay away from boards like the FTW series; They have some extra enthusiast overclocking features which cost a small amount more, but aren't necessary.