"pull out the gtx570 and try booting with the onboard gpu?" YES, you should be seeing the BIOS screens.
You can also download a bootable diagnostic to verify the system is working before you get windows (or linux) installed.
You do have the power connectors in place on the GTX570, it take two I think.
This is a great ref: http://www.tomshardware.com/forum/261145-31-perform-steps-posting-boot-video-problems