Building system; advice needed

Hello,
I'm considering buying new PC and since this is my first attempt building one on my own I'd like to make sure everything is right.

Motherboard: http://www.asus.com/Motherboards/Z87PRO/
CPU: http://ark.intel.com/products/75123/
CPU fan: http://www.coolermaster.com/product/...-412-slim.html
CPU thermal compound: http://www.arctic.ac/en/p/cooling/th...g-und-20g.html
GPU: http://www.gigabyte.com/products/pro...px?pid=4629#ov
RAM: http://www.corsair.com/cmx8gx3m2a1600c9.html
PSU: http://www.corsair.com/us/ax860-atx-...dular-psu.html
Drive: http://www.corsair.com/en/ssd/neutro...-6gbs-ssd.html
Case: http://www.coolermaster.com.au/produ...roduct_id=6813

So here are my questions or worries:

1. I would like to overclock this CPU to at least 4 GHz. However I'm not sure if this CPU/MB/Fan combination is suitable for that.
2. I took SSD because of speed, however it's expensive therefore it's only 128 GB. I don't really need much storage space, but this is a downgrade compared to my old system, so I'm considering getting 1 TB HDD purely for file storage: http://www.wdc.com/en/products/products.aspx?id=770 (WD10EZEX model). Not sure if either of them is good.
3. I've had a lot problems with PSU in the past, so I'd like to make sure that this one will be good. Also I'm unsure if it's powerful enough and whether it has all required pins.
4. Case is more or less cheapest one, I don't quite understand what's the difference between them. Also I'm not completely sure whether this setup will fit into the case.
5. I think MB/CPU/RAM/GPU/PSU have right slots/pins/etc, but it's better safe than sorry. Did I miss any parts? I don't feel like buying anything extra after this is delivered.

Thank you in advance.