Your Q: Are all the parts compatible with each other and are all the parts reliable? And is the hyper 212+ enough for overclocking the i5 2500k to around 4.5 Ghz?
All the parts are compatible and reliable. The only quirks I have is your case but we all have different tastes in asthethics. The hyper 212+ will work just fine overclocking to/pass 4.5ghz. Unless I heard wrong, I heard people can push it to 4ghz and a little beyond running stock just fine as well. I do recommend going for the Hyper 212+. It's cheap and efficient.
You chose a 800W power supply from corsair (reliable) and a crossfire/sli ready motherboard so I hope you plan to purchase another GTX 570. A single GTX 570 will be fine with a 500W and at least 750W+ is necessary for running sli [system load]. You're in the clear for sli. You're pretty much set to go.