Gaming PC build, Advice/Compatble?

Sup community?

I'm tuning in from my little cave in Sweden looking for some advice on this piece of hardware. Mainly uncertain about the power supply (want a "large" marginal so i can add/change parts in the future), and if the motherboard/processror/and the graphic card sympathise with the case and that everything fits and can be connected properly.

I've never build a computer before, fairly technical and friend with a computers nature overall. Hard? Mostly worried about what comes after it has been put together (drivers, setting the BIOS correctly)!
Case:
Cooler Master HAF 912 plus

Motherboard:
MSI Z77MA-G45

Processor:
Intel i5-3570k

Graphic Card (GPU):
MSI GTX 670 (with Twin Frozr IV)

CPU Cooler:
Cooler Master Hyper 212 Evo (CPU)

Memory/(RAM):
Corsair Vengeance 8 GB (2 x 4 GB) DDR3 1600 MHz

Power Supply:
Cooler Master Silent Pro M2 720W PSU

Hard Drive:I had something like these to in mind: Western Digital 1 TB / Seagate Barracuda 1 TB

SSD:
Not sure, been thinking of it. Is it worth it? Afterall they are kind of expensive when they're not really needed.

OS:
I've been thinking about getting a Mac OS, how would that affect performance wise for games and more heavy programs like photoshop when running on a self-built PC?
If not Mac Os, a normal windows license will be needed!

Approximate Purchase Date:
A month before Christmas or so, perhaps its better to say around Christmas.

Budget Range:
2 000 USD

System Usage:
Gaming.

Location:
I live in Sweden - Gothenburg.

Overclocking:
Absolutly, perhaps not in a while, not to happy OC'ing when the parts are all new. But later when its more "needed".

SLI:
No, i'll never bother using SLI/Crossfire.

Monitor Resolution:
1920x1080, might use a 2:nd monitor when using photoshop for example.

Additional Comments:
I want to be able to use this build as a foundation for future upgrades (I.E upgrading the parts that needs to and keep the old ones instead of purchasing everything new again).