1. At the moment, I am planning to get an ASRock B85 Pro4 Mobo and a Silverstone PS08B case. I am a bit confused as to how the USB 3.0 ports will be set out? Will I have to get a new MoBo or case? I am also looking at the Gigabyte GA-Z87M-D3HP MoBo.
The ASRock B85 will not overclock, the GA-Z87M-D3HP will. Whichever brand you choose, look at Z87 boards for overclocking. The USB 3.0 on the case has a cable that attaches to the motherboard to provide for that, it's very straight forward install. One thing to note about USB 3.0, you do not get that function until the OS has loaded drivers for it but the 3.0 headers will work as USB 2.0 until the drivers get loaded.
Your overclocking goal looks to be obtainable but the final numbers will be up to you to find (no guarantees in overclocking)
Hope it helps