First build - recommended parts for photoshop?

Hi all,

Never built my own computer before, and am trying to research what parts to get. I'm getting a little overwhelmed by all the options, so I'd appreciate any feedback!   My main use will be Photoshop. I don't use it professionally, but more like a serious hobby. Very minimal, if any gaming. No over-clocking as that kind of intimidates me lol. My budget is $1000-$1500.

Here's the parts I've picked so far and why, and the questions I have about them:

Processor: i7-3770 because it is multi-core and 64-bit, which CS6 can take advantage of.
Graphics card: GTX 460 1 Gb, supports OpenGL and good performance for its price.
RAM: At least 16 Gb, seems like many photoshop users suggest this size.
2 hard drives, either 1 SSD and 1 HDD, or 2 SSD

Questions:
A lot of people suggest dedicating a single SSD drive as the scratch disk. Since I'm only getting 2 hard drives however, will it make that much of a difference if I use the same drive for something else, for example the OS? Or does it really have to be ONLY for scratch files in order to really up the performance?
Is an i7-3770 overkill for casual (but still frequent) use of Photoshop?

Again, any pointers are greatly appreciated.