To elaborate on what Asrock tech support meant its a simple case of some monitors have weird separate skewed resolution settings until they hit the login screen where the monitor switches to its native resolution. You can usually fix the issue by simply pausing the boot process at the splash screen and adjusting the height and width options on your monitor settings until the splash screen completely fills the screen.
...unless you have a monitor that doesn't (for some obscure reason) disable your screen height and width options. *ahem* Note to self: stop buying cheap monitors! Thanks for the clarification on this! +1

Oh, and in terms of age of the chipset, while the P67 can't be considered new anymore there's still not a lot of differences between the P67 and Z77 The biggest are no PCI-E 3.0 or ability to use the on-die IGPU. Those really are the only major differences. Technically there isn't even any reason why any P67 mobo can't have a UEFI update letting it support IB CPUs, you just won't get the PCI-E 3.0. Intel as they are though will probably forbid any such UEFI update so people have to buy a Z77.
That wouldn't surprise me about Intel; but not a problem anyway, since it seems like the best time to do a system refresh is 2-3 years after the release of your current mobo when technology again offers the biggest bang for your buck.