Yes, it will POST. I am assuming that you are using the VGA output from the motherboard HD 4000 graphics. If no PCIe card is installed then the system will look for the next available graphics system which will be the HD4000 graphics. When you do decide to install the discrete graphics card, the BIOS will then default to using the PCIe card as the primary graphic card so you will need to move the VGA cable to one of the outputs coming out of the graphics card. Does your monitor have an HDMI or DVI input? Or do you need to convert HDMI or DVI to VGA to connect to your monitor? If so, then you may need to get an adaptor.
Thanks, that is exactly what I needed to know.