It could be the board but I would also suspect that maybe the power supply was marginal and the extra power draw pushed it over the edge. If you can give any model numbers off the power supply sticker or tell us what brand/model case you bought I will try to find more info on the power supply. I'm guessing that the power supply has a few years of use on it.
I took the time to download (PDF) and look at the manual for your motherboard. The BIOS has no setting for selecting a PCIe running mode. The board apparently operates the PCIe video card automatically in 1x mode (actually x1).
Even so , I noticed that the card you installed is not listed on the compatible list. That fact doesn't mean your card isn't compatible. It's just something I noticed. It may or may not be a factor with your problem.
Make sure your BIOS is set so that the "Init Display First" is showing PEG.
Also, that your "Onboard GPU" is set to Disabled.
If you have those items properly set, You should at least be able to POST and also to at least boot in standard VGA mode, assuming no other issues.
If you manage to boot, you may have a video card driver conflict if you didn't delete the old card's drivers. You need to install drivers for the new card.
Thanks for taking time to read the manual. I put a new power supply in and had the same results. The cd/harddrive was unplugged as well as everything else. The video card was removed and only a keyboard was connected. I checked all the connections so I am kind of stumped. I usually can fix'em unless their fried. I needed a new P/s for another machine anyhow. I even tried a different monitor. Ideas?